From what I've heard from others, my experience with the Amazon Prime invitation wasn't typical, but I decided to mention it since you're asking. I got the invitation at the end of 2018. After a few months of not hearing that my book was going in, I contacted Amazon and asked when. They said "it could be 30 days, 90 days, 180 days or longer." And
if it was put in, they'd let me know.

I'd been planning to go wide, but I waited because I thought my book would get into Prime. It's now been 9 months, and I've accepted that it won't happen. I'm moving the series wide in the next month.
I've never heard of this happening to anyone else, but I'm curious if it has and people just don't talk about it?
Anyway, I hope it works out better for you.