New users unable to create account

I've published a few new reports and dashboards and when sharing them to work colleagues, when they try and create a new Power BI account, they can't get past the Prove. You're. Not. A. Robot. stage of the process. It doesn't seem to matter if you choose "Call me" or "Text me", the telephone number you enter is not recognised.

I'm trying to demo this to my boss and I'm looking a bit stupid as they can't access the published reports!