Blue screen: can’t open Windows 10

I have an ex-corporate Lenovo laptop given to me when the project ended. All worked fine for 3 years on a Spectrum router in old apartment.
I moved.
I used my T-Mobile Android phone as a hotspot in my new apartment.
All worked fine.
Then I purchased a T-Mobile router and set it up. It buffered a bit, called T-Mobile and got everything sorted.
7 days later I woke up to a blue screen telling me I can’t access Windows 10
This is NOT the BSOD!
It gives me diagnostics but I tried every one and nothing works.
I have access to Command Prompt and it immediately takes me to X:windowssystem32
I switch to C:
After playing around I found some file changes on that 7th day….
Under c:usersmy nameonedrive there is a file called personal vault.lnk.
It’s 1.14MB and was created as I slept.
The next morning I could no longer access Windows 10
Any ideas how to fix this.
I can see my documents but cannot get into Windows 10 and all suggested Diagnostics failed.