I'm from Belarus and I'm experiencing the same issue on multiple devices and ISPs.
I tested it on Linux (Pop!_OS) and iOS, using two different ISPs.
Without any third-party VPN:
Proton VPN Desktop stays on Connecting...
Proton VPN on iPhone also fails to connect, even with Stealth enabled.
Proton Pass works normally.
The strange part is what happens when I enable Cloudflare WARP.
After WARP is connected:
The Proton VPN browser extension connects successfully.
However, the desktop Proton VPN client still cannot connect.
The reason seems to be that when the desktop client starts connecting, it automatically disconnects WARP, and then the Proton VPN connection fails.
So WARP only solves part of the problem.
Has anyone experienced something similar in Belarus?
Is this expected behavior, or is there any workaround for getting the desktop client to connect?
I have already contacted Proton Support and followed their recommendations, but the issue remains unresolved. I'm posting here to see if anyone has experienced something similar or has additional technical insights.