Set up my account through Facebook, now doesn't accept my login. I don't want to lose this account. How do I retrieve it?

I am not aware of the possibility to sign up with Facebook to Garmin Connect. At least I do not see it anywhere on the sign-up pages of GC now, and I do not remember seeing it when I signed up, either. Normally, you have to sign up with an email address, and if you forgot your password, you can recover it - the password recovery function is available on the sign in page of Garmin Connect (https://connect.garmin.com/signin).

This is what concerns me. Has the app recently been updated (since Jan 2020), so that this is no longer an option? Or has the link to Strava affected it?

I remember reading about this complaint probably 6 months ago.

This is what concerns me. Has the app recently been updated (since Jan 2020), so that this is no longer an option? Or has the link to Strava affected it?

I do not remember ever seeing the possibility to sign up GC with Facebook. AFAIK there is only the possibility to link FB and Google accounts to GC, but have never noticed any option to use them for signing up. But perhaps it is just my fault not paying attention enough. Did you try using your email address to recover the password? Strava does not affect in any way the user name and the password used for the signing in at GC.