New registrations don't work after upgrading to Membership 2 Pro

Hi. I have just upgraded from Membership Premium, to Membership 2 Pro. I have been putting it off for a long time due to several issues, however I was hoping it was going to be fine after I tested and retested on 2 development site versions and thought I had ironed out the bugs. However when I set up this live site, which had a lot more data because of all the members, I can not get new memberships created. For some reason after clicking submit, the webpage hangs for ages and does not fully load, so the registration doesn’t complete :slight_frown:

Please help find out why new registrations are not working, or I will be forced to going back to the faster, older version which you guys no longer support. I did not want to upgrade, but without it been supported for years, I felt I had no choice.