Hmm im having a problem even though it says how to "fix" it in the this_invoice_has_already_been_paid_error.txt file.
I've installed v2.2 with no problems, set it to run on test and created a sandbox account. I was getting the 'Invoice Has Already Been Paid' error message so i then used the text files fix.
But i still get the error (it does say in the txt file to disable it via paypal if error still occurs) but i would prefer not to disable duplicate invoice checking.
I looked at some of the older threads and i can get the payments to work if i replace
$parameters['invoice'] = substr($cart_PayPal_IPN_ID, strpos($cart_PayPal_IPN_ID, '-')+1);
in paypal_ipn.php
with
$parameters['invoice'] = $cart_PayPal_IPN_ID;
But then the IPN isnt successful (the order is made, payment sent but the order status is stuck on Preparing[iPN] and emails nor stock level is sent.
Im not using any other Contribs.
Any advice?