We all have faced this issue where Dynamics 365 keeps opening the login page in the new tab.
If we check the URL it is basically redirecting to --> https://ourwebsite.com/Auth/v2//authRedirect.html#id_token=[token]&session_state=[guid][token]&session_state=[guid]
To disable this behaviour for all the users, disable the learning path.
Set Enable Learning Path as No.
For individual user, select Opt Out of Learning Path from Personal Options.
For Internet Explorer (without changing above settings):