Happened to my Civic too. 2days after I got my car last August, the cover keep popup. Send back to Honda service center 3-4 times before they fixed it finally. Initially, They tried many methods and it didn't work. They even took another newly deliver car cover and put into my car (very unprofessional by doing that. Fuck! What the hack!). Finally the pull the ring (the one the cover clip to) to make it larger and that solve the problem. Been 6 months now without issue.

Mine is 1.5T leather. But i believe this is a defect for all new Civic-X because the ring, where the cover clipped on, is a bit smaller and therefore the cover can't properly clip on to it

The Honda service centre asked me to make a defect report with Honda (M) and I did that last year. But seem like this still happening to new cars.. so I guess Honda (M) not give a damn about this defect

Sorry, I dare not to open the cover to take a photo to show you the ring. Afraid it will not clip back again.

The ring I'm referring to is a steel bar that's is screwed to the seat. The plastic cover of the power adjuster then clip to it.