What device are you attempting to use Real VNC Viewer (or whatever they call it now) from?
Is it a desktop PC?
Either my desktop PC running Win 8.1 or laptop running Win 10 both using wired LAN connections.
As stated in last post, can connect when at the remote location using desktop PC running Win 7 or laptop running Win 10 using VNC "local" configuration (stipulating IP address) or strangely enough also using cloud configuration, ie., should be the same as connecting remotely from anywhere.
Considering the above, logic would appear to indicate that the issue is at my home connection point except that I can still connect perfectly to my other remote RPi which uses an identical setup !
Used the system extensively all last summer to the 3 devices (my own line included) while touring, worked faultlessly from all locations and proved to be very effective after the demise of MDWS last March.
Something I have not yet tried and as further process of elimination, I'll try a VNC cloud connection to the RPi with the issue from the other remote location.
You would need to obtain the IP that the Pi connects to over Real VNC and run a tracert when it works and when it doesn't, then compare the 2.
Absolutely no idea how I would get this.