Currently supporting a Microsoft Access app that's been integrated with Authorize.net for years. It works perfectly fine on multiple PCs on the same network.

However, on a few PCs, when it runs the command to send the XML file using an object of type MSXML2.XMLHTTP, it fails with this error:

It doesn't matter what the command is. Even simple "readonly" data retrieval like getCustomerProfileRequest fails.

I presume it's related to a setting or something not installed on the PCs with the problem. Maybe TLS?

Anyway, I'm not sure what to check. Any suggestions?

Thanks in advance.