This is caused by the new runtime misreporting GM_runtime_version as 1.0.999.13655
The easiest would be to override the constant yourself, e.g.
#macro GM_runtime_version "2.3.4.442"
more broadly, to run GMLive-server with command-line arguments, you’d shift-right-click in its directory in Explorer, pick “Open command prompt”, and do
.\gmlive-server.exe --runtimePath C:\ProgramData\GameMakerStudio2\Cache\runtimes\runtime-2.3.4.442
or alike.
Hullo! Sorry to necro this but since it's relevant, when putting LTS runtime versions into this macro GMLive doesn't seem to find it. I can work around this by running GMLive manually through command line in the way you describe where I can provide the full path, but also notice that removing the macro entirely still causes this issue. Do you know if the current runtime still misreports the version and/or does GMLive perhaps not check LTS cache folders for runtimes?