I used a plate solved image of NGC654 which was oriented N up E to the right. I used the N up E left tick button which corrected it to N up E left. With your image of M101 it greys out like you say and can be brought back by clicking the north button at the bottom of the screen. I see the image is nearly corrected at the proper orientation and is Plate solved. There is an Aladin manual ver 10 available on the website maybe there’s more info about this in there
Peter
British Astronomical Association
Supporting amateur astronomers since 1890