When starting Inventor 2020 the software appears to start but will freeze and display a spinning blue wheel. The software does not show as “unresponsive” and Task Manager shows activity, but the software is unusable by the end user. It appeared to be related to sign in/licensing, however none of the standard troubleshooting steps resolved the issue.
This problem appears to be caused by the Inventor 2020.2.1 update.
At this point in time the only solution appears to be removal of the Inventor 2020.2.1 update.