fundraising paypal ion has sent but donations amount hasn't updated

fundraising plug in – I’m having problems with the paypal ipn.

Some transactions have been retrying with 404 errors showing in the log file but some are showing the 200 code but the donations amount hasn’t updated.

Really struggling to get information on this.

Paypal seems to be connecting to the server and this is the successful server message:

“POST /wordpress/wdf-payment-return/paypal/ HTTP/1.0” 200 182 “-” “PayPal IPN ( https://www.paypal.com/ipn )”

but then a few minutes later this is shown:

“POST /wp-admin/admin-ajax.php?action=wdf-ipn-return-paypal HTTP/1.0” 404 27708 “-” “PayPal IPN ( https://www.paypal.com/ipn )”

Is there meant to be a file in the /wordpress/wdf-payment-return/paypal/ and if so what does it need in it?

Would appreciate any help.

Thanks

Ian