Hi XXXXXXXX;
On the back of the main unit there should be some adjustments for the door height and tension settings. You can turn them an eighth of a turn, one at a time and discover which one allows the door to completly go down.
Also please check the alignment of your roller frames. They may have become loosened and are out of alignment. Forcing the door down will cause it to derail and that is not fun to repair.
Please post any other concerns here.
Best, THS
Jack of all trades Master of a few.
#1 Home Improvement Expert. Over 30 years experience in construction, and home repairs