I have yet to see a solution to this, but about 60% of the time, customers are taken through a loop when using Express checkout. They log in, then click the PP button (either from the shipping page or cart), and it takes them to the PP site, then back to log in again. They log in, and try to do this same process, and it repeats. I've seen customers try it four or more times before just giving up. Sometimes it will work after the first loop, but not usually. However, when I force cookies, some people are then able to check out using PayPal. But then again, some are logged out and unable to log back in. This is very frustrating for the customer, and we receive emails stating so, but even moreso for the company owner.
I've removed this mod (using the newest version, but have also used previous versions and had the same issue) twice and reinstalled it, but it still does this. Not to every customer, but enough that I have spent many hours trying to figure out a solution.
Any insight that anyone could give would be greatly appreciated. Thank you!