Admin login loop

I had been using the DUO Universal plugin successfully on our website for a few months with no problems, but sometime in the last few weeks it stopped working. Now when we log in to WordPress and then authenticate with DUO, we are not able to access the admin panel. Instead, we are redirected back to the WordPress login form. We can log in again and re-authenticate with DUO, but the same thing happens again, in a loop.

I’ve tried disabling all other plugins besides DUO, but we still get the same behavior. The only solution is to disable the DUO plugin, which is obviously not our preference. With the DUO plugin disabled we are able to log in without an issue.

No technical changes have been made to the website since it was last working. I am not seeing any pertinent errors in the PHP error log, and the only logs in the console appear to be informational; there are no warnings or errors related to DUO.