It doesn't matter if you use .io or .com. Your Account (Username and password) stays the same.
So you can go to .io (where I think you are still logged in, or you could not have written the first post), look which email address you used on that account, and then use the "forgot password" function on .com to send you the link to reset and change the password. (Don't forget to check your spam folder)
PS: if your password does not work, then you have not used the same password. Maybe you have different passwords in the Mapillary app (or whatever you mean with "other applications") and on the Mapillary forum (that are two different things with different accounts and possibly different passwords).