We can't seem to get CiviEvent to work with a user's PayPal account. All works well if the user enters a CC# on our site, but nothing works if the user tries to use their PayPal account. When PayPal sends the user back to our site, the URL fails to resolve, so the user gets "We can't load the requested web page ..."
I can see from the logs that this seems to correspond to a CiviCRM error: Could not find valid value for id. Sure enough, there is no id in the URL we receive from PayPal.
Is there a setting on our end or PayPal's that I'm missing? Some way to get PayPal to use our event id?
I'm now only running the 'Clean-up Temporary Data and Files' once a day, but I still get the error frequently. I'd be grateful for any other suggestions.