hey how's it going all, I'm Andrew and I have a GLS on order that I'm super pumped about. Look forward to engaging with this forum.
To whoever is running it, I don't think you have SPF set up on your domain, so Gmail blocks anything that doesn't pass SPF and therefore signing up with a gmail account is impossible.
Easy fix, configure the SPF for the domain should take a few minutes. Just need access to your DNS management and know where your emails come from.