WHEN USING SAFARI PLEASE TRY THE FOLLOWING:
iPad / iPhone–Go to settings, scroll down and tap Safari, then scroll to “prevent cross site tracking” and turn it off.
Mac / MacBook–Open Safari and on the menu bar at the very top of the screen, next to the black apple, click the word Safari, then Preferences. On the top row of the window that opens click Privacy and uncheck the box next to “prevent cross-site tracking”.

Another alternative is to try using Chrome or Firefox instead.

This Apple site has some other ideas https://support.apple.com/en-us/HT204229 – but one that might work is:  If you can access the internet on your Apple device without WI-FI, you should be able to fill out the membership form if you turn off Wi-Fi on your device. 

In Chrome
On your computer, open Chrome.
At the top right, click More and then Settings.
Under “Privacy and security,” click Site settings.
Click Cookies.
From here, you can:
Turn on cookies: Next to “Blocked,” turn on the switch.

How to clear cookies in every browser

If you are still having problems please  Contact the Webmaster