Suddenly SSL error with S3 External


I have been using S3 external since I set my install yesterday and it had been working well. Today, in the middle of a large download from the S3 folder, a gazillion alerts popped up. Upon clicking on the Amazon folder which now is red, it says:

There was an error with message: Aws\Common\Exception\TransferException: [curl] 51: SSL: no alternative certificate subject name matches target host name ‘’ [url] Do you want to review mount point config in admin settings page?

The certificate on my site is NOT self-signed. Am I missing a step?

By the way, I had no issues yesterday when uploading those same large files, only when trying to download.

Lastly, after 5 mins, I just refreshed and it all went back to normal. Any pointers please?

Thanks so much