I didn't get any errors before, just when I hit the S key the screen reloaded but didn't display the menuDo you see any errors on screen during this time, or when you scroll up in PuTTY?
Before we go that far... how about let's do a debug... here's a version of 1.12 that has debug enabled. Don't use screen, so just start it like "sh vpnmon-r3t.sh" in a new SSH window...
Wait until it gets to the timer... hit "s", and after a few, just CTRL-C out of it... then If you could copy and paste the results from this into a text file, and please send it over to me? Then I'll look and see if there's anything weird about how your router is interpreting this vs. everyone else. It's not unheard of that certain routers have more issues with certain things that other routers don't seem to care about. It could be just that.
Code:curl --retry 3 "https://raw.githubusercontent.com/ViktorJp/VPNMON-R3/main/vpnmon-r3t.sh" -o "/jffs/scripts/vpnmon-r3t.sh" && chmod 755 "/jffs/scripts/vpnmon-r3t.sh"
No problem, will give it a try and send the output through to you shortly
If it helps, I'm using an RT-AX88U with the latest firmware from RMerlin (3004.388.6)