NopCommerce 4.0 Scheduled Tasks not triggering: "Underlying Connection was Closed"

Some background:  I have a two store installation of NopCommerce 4.0 running on IIS 8.5.   To handle the multiple SSL certs, I am using SNI.  Everything appeared to be working correctly.  

The site has been live for about 5 days now and I've noticed that none of the Scheduled Tasks have been running. I've run these tasks manually.  The Delete Guests and Send emails tasks work when manually triggered but won't run automatically.   The "Keep Alive" task fails with a "The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel." error.  Looking at my Error Log, I see that error happens close to every minute (the scheduled frequency for send e-mails).  

I'm not sure if I set up my bindings incorrectly or what else could be causing this issue. Any suggestions would be most appreciated.

Thanks!

Please do not duplciate forum topics (deleted)

I'm not sure what part of this was a duplicated / deleted post.   I searched the forum for "NopCommerce 4.0 Scheduled Tasks not triggering" as well as "Underlying Connection was Closed", "tasks not triggering" and "multi store tasks not working"  and saw nothing regarding this.  

If there a previous post related to this issue, please let me know what it is.

I am having the same issue. How did you end up fixing it?

thanks!!

Some task not running problems is the config of store host name and its access on the service
Not sure if it is the same issue but check that first
https://www.nopcommerce.com/boards/topic/78057/all-scheduled-tasks-fail-when-running-automatically-but-not-manually