I can't change my primary e-mail address

Every time I try to change my primary e-mail address I receive the following error:

Logged in user or user to be modified is invalid or blank.

So I created a new Manager user with my new e-mail address, activated the account, transferred admin rights to my new account to become the primary, and removed my old primary one. Now I can't add a phone number because it's still associated with my previous primary account and I still can't add a new e-mail address due to the same error.

EDIT:

I'm using Chrome Version 86.0.4240.183 (Official Build) (64-bit) on my Windows 10 desktop. I then cleared all cookies, cache, and etc. in Chrome and still had the issue. I then tried logging in an incognito window and had the same issue.

Then in an administrative CMD prompt I ran:

ipconfig /flushdns

netsh winsock reset

shutdown /r /t 0

When my computer came back on, the above troubleshooting steps didn't work. Firefox, Edge, and IE had the same issues as well and I even cleared their cookies, cache, etc. for good measure. As a last resort I tried on my Android phone's Chrome browser with the same browser troubleshooting steps, no dice.