Error while running the 'Keep alive' schedule task. Too many automatic redirections were attempted.

I faced this error with below detail.
I could not figure out what's the problem.
I checked store setting and store URL is in a correct format like http://domain.com/

System.Net.WebException: Too many automatic redirections were attempted. at System.Net.WebClient.DownloadDataInternal(Uri address, WebRequest& request) at System.Net.WebClient.DownloadString(Uri address) at Nop.Services.Common.KeepAliveTask.Execute() at Nop.Services.Tasks.Task.Execute(Boolean throwException, Boolean dispose, Boolean ensureRunOnOneWebFarmInstance)

It's looks like there are many redirection happen to your any plugin. Like as Site A -> Site B -> Site C or Http -> Https
Check this link may be helpful for you https://stackoverflow.com/questions/26654369/why-im-getting-exception-too-many-automatic-redirections-were-attempted-on-web

What version of NopCommerce?
Are you using SSL?  (http:  or https:) ?
If you are using SSL, then be sure your setting for store URL uses https:// .../

New York wrote:

thank you for your reply, I've checked those settings. nopcommerce version 3.9, I am using SSL, and store URL is https://.../
the problem still exists.
is there any way to check some logs and etc?

What happens if you use  a browser and go to
https://yourstore.com/keepalive/index

New York wrote:
I received a 404 page, and the log:
Error while running the 'Keep alive' schedule task. The remote server returned an error: (404) Not Found.

when I use something like
/keepalive/index/8
or
/keepalive/index/6
I receive a message "I am alive"

any idea?

I'm having the same issue using 3.8 when I tried setting up a staging server anew. Any ideas? I tried the KeepAlive/Index/8 solution with no luck. I look in the log table and get the error.