Here's what I'm doing, which I think is what you describe above:
* Go to
mfonline.dk/registrer
* Click the "Gratis" plan
* Redirected to
mfonline.dk/membership/plan/login/1
* Click the Facebook Login button
When I do that, the following URL redirect chain happens in the browser:
* The first 3 URLs in there are how JFBConnect authenticates the user with Facebook
* The 4th URL is the proper redirection that JFBConnect is trying to do to send the user to the JomSocial registration page:
mfonline.dk/component/community/register
* That URL is being automatically redirected to the PayPlans select plans page though. That's not being done by JFBConnect.
That is how the loop is occurring. If I go directly to the 4th URL about (the Register page for JomSocial), I'm seeing the same behavior. Something is forcing the user to be redirected back to PayPlans outside of JFBConnect. My guess is that it's another PayPlans plugin.
Even the page you say we should go to,
mfonline.dk/netvaerk/register , doesn't work for me if I go directly to it.
With all that explanation, and understanding what you're expecting vs what's happening more, it's worth pointing out that we have many users using JFBConnect and PayPlans together. However, I don't know if I've seen any of them using the same flow you have setup where the user picks a plan,registers with Facebook and then continues with their profile creation.
All other sites have a Facebook login which creates the account and then redirects the user to the plan selection page.
If you can switch to that flow, my guess is things will work more seamlessly. JFBConnect and PayPlans don't have specific integration for each other, so there's not a method for either to know what the other is doing and I think that's where you're running into issues here.
I hope that helps explain some more, but if you have any other questions, just let me know.
Thanks,
Alex