Membership Registration Acces Links redirecting to Homepage

Hi there. I have been using S2Member pro for a number of years and have always used the membership registration access links to send to customers to set up their own account when they have paid via invoice rather than online. These links now only seem to direct to a registration form if I’m logged in and when not logged in they direct straight to the homepage. This was first noticed today. Any suggestions as I don’t really want to have to create new accounts manually for every customer that pays this way.

Thanks in advance,