Taxumo provides three ways of signing up:
The "traditional" email+password combination.
Using your Google Account
Using your Facebook Account
We've seen that most of the confusion in logging in comes from people who signed up using email+password (#1) but they're trying to login via Google (#2), or vice versa.
If you don't remember how you signed up, try both methods. One of them should work.
If neither work, you might not have completed the sign up process. In that case, please do signup again. Thank you!