It seems like it keep redirection to login page when you trying to register.

I've checked in your current menu structure, it seems like all the Easysocial dashboard menu item you also set to only 'Registered' user can access.

I already help you created a hidden menu for Easysocial registration, mean public user can able to access your registration page now.

It should work fine now without Payplan enabled.

Then I try to re-enabled back those Payplan plugins from your backend, I noticed it always show the pop-up and can't register it, you can check my attached screenshot below.

I suspect something is not configure correctly from Payplan setting, perhaps you can consult with Payplan developer regarding this and see how it goes?