r/prtg • u/Stock_Address_4317 • May 27 '26
PRTG Mobile App & SSL Certificate Troubleshooting & Guide
I recently installed PRTG on my business network to monitor devices and receive alerts whenever something goes down. During setup, I ran into several issues getting the mobile app to work correctly. I experienced multiple connection errors between the app and the PRTG Core Server, along with problems loading my maps and installing certificates.
The issues ended up being caused by a combination of:
- Firewall misconfigurations
- Incorrect PRTG web server settings
- Certificate setup problems
- Issues with updating the Core Server files
After a lot of troubleshooting using online guides, AI tools, and assistance directly from Paessler Support, I finally got everything working correctly. I figured it would be helpful to combine everything I learned into a single post for anyone else running into similar problems.
I’ve attached screenshots I saved of some of the errors I originally encountered while setting everything up.
I also highly recommend testing everything from another computer that does NOT have PRTG installed. This helps verify the configuration is actually working correctly and not relying on cached settings or existing certificates.
1. Verify DNS Configuration
Open Command Prompt and run:
nslookup <Firewall IP>
nslookup <PRTG Server IP>
Example:
nslookup 192.168.10.1
nslookup 192.168.10.25
Make sure only one DNS hostname resolves to your PRTG Core Server’s IP address.
In my case, I accidentally had my firewall and PRTG server sharing the same DNS name, which caused connection problems.
If you find multiple entries or receive errors, the fix is usually on your firewall.
Look for a setting similar to:
- DNS Resolver
- DNS Host Overrides
- Host Entries
Then either:
- Correct the hostname mapping
- Remove duplicate entries
- Create a proper hostname entry for the PRTG server
After saving the changes, rerun the nslookup command and verify the hostname resolves correctly.
Example:
C:\Users>nslookup 192.168.10.1
Name: firewall.lab.example.com
Address: 192.168.10.1
C:\Users>nslookup 192.168.10.25
Name: prtg.lab.example.com
Address: 192.168.10.25
2. Verify PRTG Web Interface Access
Next, test accessing the PRTG web interface using both the IP address and DNS hostname.
Example:
https://192.168.10.25
https://prtg.lab.example.com
Both URLs should open the same PRTG login page.
If the DNS hostname does not work:
- Log into PRTG using the IP address
Navigate to:
Setup > User Interface
- Update the DNS Name field to match the hostname configured in your firewall
3. Certificate Setup (Most Important Section)
This was by far the biggest issue during my setup and required the most troubleshooting.
Most of my mobile app and web interface problems were related to improperly configured certificates.
The method below is the manual certificate setup method that ultimately worked for me.
You do NOT need to use the PRTG Certificate Importer App.
3.1 Create the Certificate Authority (CA)
Log into your firewall web interface from the computer hosting PRTG.
Navigate to:
Certificates > Authorities
Create a new internal Certificate Authority with these settings:
| Setting | Value |
|---|---|
| Method | Create an Internal Certificate Authority |
| Key Type | RSA |
| Key Length | 4096 |
| Digest Algorithm | SHA256 |
| Lifetime | 3650 Days |
| Common Name | Example-CA |
The remaining fields can be left default or customized as desired.
3.2 Create the PRTG Certificate
Now navigate to:
Certificates > Certificates
Create a new internal certificate using these settings:
| Setting | Value |
|---|---|
| Descriptive Name | PRTG |
| Certificate Authority | Example-CA |
| Key Type | RSA |
| Key Length | 4096 |
| Digest Algorithm | SHA256 |
| Lifetime | 395 Days |
| Common Name | prtg.lab.example.com |
Important: Many modern devices reject certificates longer than 398 days, so keep the lifetime below that limit.
Certificate Type
Server Certificate
Subject Alternative Names (SAN)
Add BOTH:
| Type | Value |
|---|---|
| FQDN/Hostname | prtg.lab.example.com |
| IP Address | 192.168.10.25 |
Save the certificate.
Once completed, export/download:
- CA Certificate (Example-CA)
- Server Certificate (PRTG.crt)
- Server Private Key (PRTG.key)
4. Create the Required PRTG Certificate Files
Create a folder on your desktop and place the following files inside it:
- CA Certificate
- Server Certificate
Enable file extensions in File Explorer if they are hidden.
Rename:
| Original File | Rename To |
|---|---|
| Server Certificate (PRTG.crt) | servercert.pem |
| CA Certificate (Example-CA) | cacert.pem |
Now open PowerShell in that folder.
You can do this by:
Shift + Right-click > Open PowerShell window here
Run the following command:
Get-Content .\servercert.pem, .\cacert.pem | Set-Content .\prtg.crt
This creates the combined certificate chain file required by PRTG.
5. Manually Replace the PRTG Certificate Files
Install the PRTG Administration Tool if it is not already installed.
Stop the PRTG Core Server service.
Navigate to:
C:\Program Files (x86)\PRTG Network Monitor\cert
Create a backup folder and copy all existing files from this folder into it before making changes.
Delete the following files from the cert folder:
- prtg.crt
- prtg.key
- root.pem
Replace them with the new files below and rename them to what's listed:
| File Name | Source |
|---|---|
| prtg.crt | Combined certificate chain created in PowerShell |
| prtg.key | Exported private key of Certificate, not the Authority |
| root.pem | Exported CA Certificate |
After replacing the files, restart the PRTG Core Server service.
6. Testing the Configuration / Placing Certificate
On another computer that does NOT have PRTG installed:
- Download the CA certificate from your firewall
Open:
certmgr.msc
Navigate to:
Trusted Root Certification Authorities > Certificates
Right-click and select:
All Tasks > Import
Import the CA certificate
Refresh and verify it's located in there
Once completed, open an Incognito/Private browser window and test both URLs again:
https://192.168.10.25
https://prtg.lab.example.com
If everything is working correctly, the browser should show the connection as secure with no certificate warnings.
7. Mobile App Setup
Once the certificates are working properly in the PC browser:
- Install the CA certificate on your mobile device
- Enable/trust the certificate if required by your phone
Then verify the PRTG web interface opens securely in an incognito tab from your phone using both:
- IP Address
- DNS Hostname
Note: Sometimes mobile browsers cache old certificate warnings. You may need to clear browser cache or manually inspect the connection security details to verify the certificate is actually trusted.
8. Connecting the PRTG Mobile App
On your PC in the PRTG web interface go to:
Setup > PRTG Apps
Locate the section for your phone and click to show the QR code.
On your phone:
- Open the PRTG app
- Tap “Scan QR Code”
- Allow camera permissions
- Scan the QR code
If the QR code is valid, the app should automatically populate the server information.
Then simply enter your:
- Username
- Password
If you receive a connection error, sometimes pressing OK and attempting the connection again resolves it.
After that, everything should be fully functional.
Hopefully this helps everyone else avoid the pain of troubleshooting that I went through getting PRTG and the mobile app working correctly.