a customer reported this "Invalid signature" error earlier today. The payment was confirmed by email in the usual way but because the process didn't complete cleanly the payment was not applied in the AwareIM app.
I did some investigation and discovered the customer was not using their merchant ID - rather they were using the older method of their PayPal email address. So could this be the issue.
AFAIK this only seems to be a problem if they are using Apple kit (Macs and or iPhones)
My SSL certificates have not changed and not due for renewal until May
