Hi! Im having similar problem but when trying to select the domain a different messeage pops up.
First of all, when i type the domain, and i click on buy, this page appears (see first picture): "First name must not contain special characters" and an option to edit my store information and of course i cant proceed to buy the domain without solving this problem.
When i click on that button, it redirects me to this page (see second picture) with all my store info. However, i can't see what is it that has a "special character". Everything seems normal to me. Any Help please?!?!?!
First name must not contain special characters