Kicked out of Blended Retirement System?

BLUF: Has anyone been removed from the Blended Retirement System (BRS), and if so, how did you get reinstated?

Flashback to Fall 2017, I am a freshman ROTC cadet still learning how to tie my boots. I get asked at some point whether I want to be part of the legacy system or the BRS. Obviously, I opt into the BRS. As I recall, I made this election by simply clicking a button on myPay. I’ve received matching contributions since then without issue.

Flashforward to February, my TSP match stops. After multiple inquiries, finance is now saying that DFAS has no record of me opting into BRS. The tab on myPay where I made that initial election is gone and I can’t find any evidence of that election in my IPerms.

Questions:

1. What was the official enrollment process for BRS? Was there a form or record beyond the DFAS opt-in online on myPay? Looking for anything that would have been evidence that I made this election in the past.
2. Has anyone experienced this or a similar issue and successfully resolved it?