Try manually resetting your plugins (no Dashboard access required). If that resolves the issue, reactivate each one individually until you find the cause.
If that does not resolve the issue, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), navigate to /wp-content/themes/ and rename the directory of your currently active theme. This will force the default theme to activate and hopefully rule-out a theme-specific issue (theme functions can interfere like plugins).
That will get the login form working again. If your username and password are still not recognized, try https://wordpress.org/support/article/resetting-your-password/#through-phpmyadmin which will walk you through changing your password directly in the database and you’ll see the username along the way too. (you’ll find phpMyAdmin in your hosting account’s control panel)
This was quite helpful, thank you for your quick reply!