Verify the bank being selected -- There may be several different versions of the same bank in the Add Account bank list, so be sure you're selecting the correct one. If you're not sure, compare the URL's shown for each bank.
Verify your login information – Type your password/PIN into a text application to ensure you don’t have any typographical errors. Then, copy and paste your login information into Simplifi to ensure accuracy.
Verify your login at the bank’s website – Try to sign in to your bank’s website using the same login credentials to ensure you've not locked yourself out of the account and that the credentials are still valid.
Check for an app-specific password – Some banks require users to use a specific app-password when connecting to a third-party. Check with your bank to see if you need to use an app-specific password.
Update your credentials – Try temporarily updating your password at your bank's website and then try again to connect to Simplifi.