Twitter blocking the request. When does this happen? Are you monitoring the HTTP traffic by any chance? If so, it's the TLS fingerprint blocking you.
A couple more things you could consider adding are that the username and password are copied to the dashboard with this new 'generate cookies browser' login method. Because I can't manually open the account details in TD because a pop-up to generate cookies is blocking it.
Sure, I thought it already happened though!
Currently, I export the accounts that encounter this login error to a new instance and then copy-paste the auth token. Additionally, I open a notepad to export all usernames and passwords I need for manual login.
Have you tried the new automatic login? The browser login should not be necessary now (unless you want to use browser cookies for whatever particular reason