Hi! Just wanted to say thanks and this solution worked for me with a similar issue.
Even with the Windows Defender Firewall turned off, in the Unreal Vcam app I got a message “Failed to Connect Unable to connect to 192…”
In Unreal Editor > Pixel Streaming I clicked Stop Signaling Server. I left Streamer Port as the default 8888 and changed Viewer Port from 80 to 71
I clicked Launch Signaling Server again
In the Unreal Vcam android app, I ignored the existing connection, and I created a new connection by entering my IP address and changing the 2nd line from the default 80 to 71
I don’t understand why it worked, but it did!