Dallas here from the Shopify Social Care Team.
I went onto your website and created a test account and it seemed to work on my end.
Is this something that you have just noticed or have you heard from customers as well that they haven't been able to create an account? If you're just noticing this on your end it could be related to cache. That would mean that you'd want to clear the cache in your browser which could be causing the issue in creating a customer account. This is a great link on how to clear the cache for any browser.
If you are finding this is happening for others or on other devices could you gather some information for me? That will help me decide on what I should do in regards to the next steps.
That information should help me to have a bit of a better grasp of what is going on and how I can help us work towards the best way to get that fixed.