Hostname/IP does not match certificate's altnames

Hello:

You mention that your API is REST, but are you also using this domain for a new HTTP API?

Can you send me your account id and domain name (as a private message) and I can confirm with the team if there's an ongoing issue.

Regards,
Bob

I'm having this same issue.
This occurs only when I am trying to post/get to sandbox.
https://sandbox.sellingpartnerapi-na.amazon.com/vendor/directFulfillment/shipping/v1/shippingLabels/2JK3S9VC

These calls were working last week. I know that someone updated something with the vendor API java classes we use, but this is working with the product API URL, plus there are unit tests that ARE succeeding when pointing to sandbox.