Can anyone please assist me with proper coding for a Preventive Exam for Medicare Advantage/Medicare +Blue plans?

I am being told that a preventive visit is covered, as in 99396 or 99397 but I cannot get claims to scrub with these codes. Just recently I have started getting rejections and / or patients being billed for these visits. Plan states there is a preventive code but they wouldn’t give it to me.

Please help!..Thanks so much