Make sure the account, Adobe ID, you are using to Sign In with is exactly that same as listed on the Adobe website and tied to a valid credit card.
Check the Host file that LR isn't being redirected when it is trying to validate your subscription.
Yes, I've verified that the Adobe ID I'm using is the same one as the one listed on the adobe website. I know this is the case because I've signed out and signed back in to both CC and the website multiple times.
I also used the Limited Access Repair tool to reset the host file and when that didn't work, I deleted the host file altogether.
I found the Limited Access Repair tool while following the instructions on the second link: https://helpx.adobe.com/x-productkb/policy-pricing/activation-network-issues.html
There was a post recently about the same exact thing or something very similar. Turned out somehow that person had 2 Adobe ID's almost identical.
Here's a link to that thread.
So I suggest you contact Adobe directly either through the Chat option on the Adobe support page or if you can find a phone number for them, make a call.