Welcome to the Community.
Have you had the chance to test it out from a different browser? It's also important to check that there are no spaces before or after the actual SIM card number to avoid any errors.
Thanks for posting and welcome to the Community!
At what step do you get an error, and what does the error say?
Also, are you entering the 20 digit number that starts with 8930 without any spaces?
Let us know!