You said you are able to log in using the browser extension?
If so, you can open the browser extension and click on the account avatar icon (colored circle with your initials) in the upper right corner (shown circled in orange in the screenshot below):
This will open the Account Actions screen, shown below. Please look at the account that is labeled “active”, and pay close attention to the email address as well as the server name (bitwarden.com or bitwarden.eu) shown in gray font just below the email address:
When you attempt to log in to the Web Vault, make sure that you use the exact same server, as well as the exact same email address (matching the server and email address shown in the browser extension’s Account Actions screen).