I've had the same issue today after I first installed Ajenti 2 on Ubuntu 22.04.2 LTS.

This is the work-around I found for elevating:

1. Open two instances of the login page. 
2. Login to one of those pages first before the next step.
3. On the second login page, replace the word "normal" in the URL with "sudo" then enter your password there and submit.

I don't understand why it's redirecting automatically without waiting for user input for elevating, but I hope this helps.