X40 ultra carpet

My recently purchased x40 ultra does a poor job cleaning carpet. I've set maximum suction and had the vacuum clean 2x but it still leaves crumbs and cat hair. It's a low pile carpet. I've checked the roller brush and it's clean.
Any suggestions?

Very common problem with these. The rollers dont activate and hit the floor. I've sent two back. Waiting on the 3rd. After that no more dreame products.

On the off chance, have you checked the suction tube area in the machine (it’s sort of hidden behind the cleaning brushes) as well as the suction tube in the base? I thought mine wasn’t able to clean the rugs until I realized it had sucked up a tiny clear plastic bag that was nearly completely blocking the suction pipe area.