Sure thing.
I apologise. We all need to learn to be better community members, now. And every little helps.
This was fixed simply by restarting the server.
Nothing wrong with Ray's code. Or with eCart.
Restart was all it took.
Took me over a week to get to that.
First went to "authorize.net"; then "TSYS". No help.
Then thought to investigate on Google for any similar errors in PayPal
After wading through so much fluff and irrelevancies, eventuall zeroed in on the following error as the most likely:
"Cause #3 – Your server is blocked for external CURL calls.
Solution: This needs to be checked with your hosting service since this configuration cannot be modified without administrator access to the machine. We suggest you get in touch with your hosting provider and ask if there are any restrictions on cURL calls or even firewall rules to block any outgoing requests."
Went to my server company and they were no help because my PHP 7 specs were fine.
Evetually, I just thought, why don't I just restart the wretched server, just in case.
So went into Plesk and hit appropriate button. Waited 5 minutes with bated breath. And kaboom.
Everything fine.
So ... if stuck, try restarting the server. Especially with as fine a standard of coding as Ray has put in his software.
Thanks. And let's all remember that sometimes switching gadgets off and then on again really does work!!!
Please be well.
KAB