Can't log into account after reset

So a couple weeks ago I decided to do a factory reset on my phone as I've done numerous times before, but for some reason this time around I've been unable to access my account in Deck Heroes. I'm logged into my GMail account as usual and I've even downloaded DH through the email's Playstore account, but when I go to the in-game Settings my email address doesn't show up in "Link" or "Switch Accounts."

I've spent the last couple of weeks exchanging emails with IGG trying to fix this, but it feels like they're giving me the run around with the same directions to "Link/Switch Accounts" and I'm reaching my wit's end. At one point they told me they could transfer the info from my previous account with the IGG ID/email I provided them, but this recent representative (for some reason they think it's a good idea to switch reps every few responses) now says they can't do it.

Anyway, since I'm not holding my breath on IGG being of any help at this point, my only options are to either give up or figure out what's going wrong with my Playstore/DH that it doesn't recognize my linked email. Has anyone had a similar issue that they were able to resolve? I've already tried reinstalling the game and relogging into my email account countlesss times.