API - Constants - ANetEnvironment - Endpoint Instability

[nccCFD]

I manage several sites using the A.Net PHP SDK; all ran the forked PHP 8 SDK until the official release in September. I've changed all to the official release.

One site is experiencing intermittent failures, no communication at all with A.Net. Duration of 30 to 40 minutes per outage. If I change the api endpoint in the Constant file, connection is immediately restored. It'll work for an hour, a day, a week then fail again. This has been ongoing for about a month. The last few days, I'm having to rotate end points three or four times per day.

The api2.authorize.net end point specified in the SDK works for the least amount of time. https://api.authorize.net/xml/v1/request.api seems to work longer.

I can not seem to find any clue as to why this is occurring; and why to only one site. Every other site I manage is just fine. Several are on identical servers as well.

I've whitelisted all A.Net API Endpoint IP's, checked that the most recent certs.pem file is in place, troubleshot anything I come up with with server configuration, etc. I'm at a dead-end; hoping someone in the community may have had a similar experience and could point to something. Thanks!