I’ve got SQL Server 2019 Developer Edition installed on my Windows 10 Professional machine. In the last couple of months my Windows profile became corrupted, so I had to abandon it and create a new Windows profile. (Not something I want to do ever again.) What I didn’t realize is now I’ve lost the ability to login into my SQL Server default instance. For whatever reason, although my new profile is in my local Administrators group, my new Windows profile isn’t. (I’d love to know why not – so if anyone knows, please fill me in.)
I’ve been looking around for ways to regain access to my SQL Server. Here’s a promising looking website Recover a lost SA password.
Another website which goes into more details, and eventually helped me solve my problem, is Connect to SQL Server when system administrators are locked out
Doctor Who 