I tried to connect my Google account to iNaturalist on my laptop so i can upload observation photos from Google Photos like i do when using the Android app.
A message appeared saying that my account was already connected to another user.
This is not possible, if anyone but myself had tried to use my Google account for anything i would have been informed by Google and no one would have been able to guess my 128 completely random letters, numbers and characters password manager generated password for my Google account anyway.
It’s possible that you might have made a previous iNat account that you forgot about (I think this has happened before). But I think you will need to email help@inaturalist.org - they may be able to see what iNat account is connected to your Google account and work from there.