Curl 28 error – auth.net payment

we have had a payment error for the past 3 weeks, and been stumped with upgrading, downgrading, error checking everything. Cent OS, Curl, PHP, WordPress, Apache, etc..

Finally, we had to hire a sysadmin at $$$$ to trace the issue.

When a customer goes to the payment page, they enter their info, and hit submit. The payment gets taken off their CC, so we know the curl request goes out, but, intermittently, the payment response gets blocked coming back.. so their account doesn’t get activeated.

This happens to the same customer, same IP, same browser, etc. both ways.. i.e. sometimes they succeed on first payment, but not on second, and vice versa. same product purchased.

Ultimately. the expensive sysadmin contractor has narrowed it down to Wordfence. Which we have had for a few years.. what happened? we are on the latest version as of July 1, 2020. php7.4, etc.

1) I’m upset that I paid for a plugin that I can’t use
2) I’m wondering what I will use instead.

I’m asking for any suggestions of what to do? what’s blocking it? what to look for.. oh FYI, i’ve already made some of the rules less stringent.. also i block naughty countreis..