@Riley_S 

This is the link to a thread I read back then where someone else had the exact same issue as me. People were able to fix their issue by creating a TP Link account. As well as this 15 character thing mentioned in the thread. But like I said, neither of those solutions would help me because I ALREADY had a tp linked account and a password that was nowhere near 15 characters.

https://community.tp-link.com/en/home/forum/topic/166782?replyId=463060&utm_source=Subscription&utm_medium=email

When I open the Tether app it shows my new booster as a "local device" and the router as a "cloud device". I would guess that's because I am connected to the booster first. Anyways, when I click booster it goes right in like it used to for the router years ago. If I select the router I get the following.

"Enter login password (not your tp link ID password) you have created to manage your device"

I never made any password OTHER than the tp link ID password. I kept the factory setting password because it was convenient to have it on the card printed. 

I tried both many times neither of them work. Tried "admin" but that doesn't work either. I can't really track what I've tried because it will threaten to lock me out after a few wrong attempts. 

But again it really makes no sense how the app wont let you interact with the router at all without this mysterious password. Yet on a browser I can just bypass the entire thing by logging into my tp link account. Although it still does ask for this mysterious password on a browser. It simply allows me to use my account as an alternative. Which is silly because on the app I am already logged in. It should work the same way but it doesn't.