It wasn't possible to connect, are you sure the URL is correct?

Hi, 

I’m trying to send TEST Event to my newly created server with ssl certificate activated. But, I always see this error 

It wasn't possible to connect, are you sure the URL is correct?

But, I can access the endpoint using Post Man without any issue.

Please, advice what should I do to diagnose this error. 

Any help is appreciated. 

Thanks, 

JA