Maybe double-check that your client is trying to authenticate with the correct credentials. I’ve seen some cases on Windows update in which the windows client forgets the old credentials used and tries to pass the MS account instead. midclt call smb.status AUTH_LOG | jq should show some details.
FYI, trying to connect with the main account (root + password, so I guess should not be considered a guest account), same account I used to connect from, it wouldn’t let me log.
Had to update another account with email + new password and problem solved.
Thank you fchk for the tip.
This is the answer to a lot of people’s questions about why they can’t login after updating a router or other things. I was stuck for a couple of days. I could ping and guest, but not login. I will post this where I saw others struggling and not getting answers. Thank you!