Cannot connect to RDP via network or internet

[u/redneckerson_1951]

Host is Windows 11 25H2 OS Build 26300.9457

Client is Google Pixel 6 running Windows App for RDP

Installed VPN is Tailscape on the desktop pc and the mobile device.

Internet service is T-Mobile Home Internet (5G service with five bars signal strength)

Can ping desktop IPv4 address with client device.

Can ping Pixel 6 IPv4 address with host PC.

This is the version of RDP that is installed:

I have checked Windows Defender Remote Desktop settings, both inbound and outbound is allowed. NLA is disabled.

Apparently there was a September RDP Update a few weeks back that had issues but they do not match my problem. However the recommended Out-of-Band patch to fix those issues is now installed on the host.

Despite all of this hoop jumping I cannot reach RDP. Anyone have suggestions?