Same problem tonight, have just gone to a Family subscription and couldn't add one family member because they can't register for an account on the PC. Failed with both Firefox and Edge on Windows 10 on two different computers. Tried on Android phone with same result.
Re: Can't create account; sign up page continuously loading after pressing sign up
Had the same problem, you need to dowload a program called "TunnelBear" (https://www.tunnelbear.com) and trick it to be in anouther country like US for example, although Germany will give best internet speed but don't put it if you don't know German. When you do that turn TunnelBear of since you have 500MBs a month or (1GB extra if you tweet about it) and those 500MBs are more then enough to trick your internet connection or websites that don't comply because of what coutry you're in here and there. Hope this helps and that I'm not late! Have a nice day!