API Expired SSL certificateAnswered

No changes to the code were made from our end. 
Issue started happening last week, we received customer complaints who attempted to use our license portal.

All api calls returning bool(false) if called from server. Even ( limelm.test.echo ). 
Also tested request in Postman. Postman returns SSL Error: Certificate has expired.

Tested both cases by disabling verification. that seems to fix the issue. Could not find anything about SSL certificate in documentation.

Could you help resolving this issue or pointing to correct information in documentation? 
Thank you in advance.