Sorry to hear that. There are a couple of things that you can try.
Firstly, if you forgot your password you can reset it here: https://simplywall.st/resetpwd
Another reason you might be having trouble is that you actually have created two accounts. This happens as you might use a Social Sign in (ie Facebook or Linkedin) once and then created a separate account using an email and password directly on our site.
If you think this is the case you can log out by accessing your profile, simply hover your mouse over your name in the top right hand side of the site:
If you still are having trouble submit a request and we will be happy to help out.