Failed to download the image!  Error Unable to complete SSL connection.

just tried /sil http://image.url/pic.jpg

Please try a different URL.

I have the same issue...

i have try a lot different URL 

but same error...

Tried hundreds of images, same issue.  Something with CentOS 8 perhaps.

I switched to Ubuntu and this fixed the problem

So I found an actual http link instead of https and that worked
but not if I leave the https
Must be a simple change/fix to allow https downloads that we can't figure out what it is

Merged post

There are loads of discussions on unity forums about this error in Unity https://www.google.com/search?q=centos+unity+unable+to+complete+ssl+connection+site:forum.unity.com&sxsrf=ALeKk01wCwNEIwqL_Tj0OD2L3tKLrCByQQ:1597939680789&sa=X&ved=2ahUKEwjh166YlarrAhUSrp4KHf2DAZsQrQIoBHoECAUQBQ&biw=1440&bih=757

Merged post

I found the fix!!!

Unity only officially supports Ubuntu Linux, so it is looking (and failing to find) the certificate store where it would expect it to be. You can work around on Fedora/CentOS by creating a symbolic link:

mkdir -p /etc/ssl/certs && ln -s /etc/pki/tls/certs/ca-bundle.crt /etc/ssl/certs/ca-certificates.crt