I’m not a Windows user myself, though I’ll try to suggest a few things:
Have you tried restarting your computer? This can sometimes fix minor software glitches.
Is the k6 binary in the directory C:\Users\LMPH>? If you created a binary with the dashboard extension, you might have it in your directory, and it’s not the k6 that was installed with winget install k6 --source winget.
If that does not help, as I would expect you have already tried and checked this, can you share a few more details: