I am in the same position, I run Windows 11, when I did a small test, say a month ago, everithing was working fine but now (that I need it) it doesn't recognize the extension anymore. The old extension had turned into the "legacy" variant and I had the new one too; anyway I unsinstalled and reinstalled them multiple times, removed any other extension, reinstalled Power Automate, nothing seems to help. I even tryed with a fresh install of Firefox, just in case the old version had compromised Edge somehow, but it showed the same error: (the picture is from one of my Edge attempts)
If I go to the extension manager, in developer mode, I can have a debug console for the service, where a waring and an error keep coming every couple of seconds:
