Paypal Standard

Hi

Can anyone give me or point me at a definitive way that Paypal Standard should be set up. I look after several opencart stores, all setup the same way with teh same base version (1.5.5.1) but some with extra extensions. The problem with one of the stores is that Paypal keeps throwing a wobbler. Customers are getting to Paypal (well mostly anyway!) but then all goes to pot, some orders work, some dont show in Paypal at all, but some do but say they failed or are in IPN retry. So teh question really is what should and should not be set in Paypal for standard to work. Does 1.5.5.1 use PDT and if so where do I put the code. Once I get a complete answer I promise I will document it and stick it on here somewhere.
thanks
Paul

Are they all hosted by the same company? My IPNs would not work, I tried everything, then I changed server and now they work fine, so perhaps it is a server problem in not receiving IPN callbacks.

Typically there is just information missing and/or statuses are not set correctly. IPN is built into the Paypal Standard and there is no need to mess with the ipn URL on the paypal side. There are more people with successful paypal standard experiences than not.

Hi, yes all sites are on the same host. What should the URL be on the Paypal site for
return address and IPN URL are set to http:shop.mywebsite.com, PDT is turned off, auto return is on.