At least on my end, this is what my .uproject looks like:
"FileVersion": 3,
"EngineAssociation": "C:/Program Files/Epic Games/UE_5.5",
"Category": "",
"Description": "",
"Modules": [
{
This is pointing to the Epic Games Launcher version of UE 5.5 . It opens the editor just fine if pointed here. But UGS doesn’t seem to accept this. Same error