Payment after activate SSL - pages looping

Hello Everyone!
For more than 2-3 weeks and I am trying to solve my problem. Search, Read articles and test various solutions but no avail.
I am using:
nopCommerce 4.5.3
Linux -Debian
NGINX
MYSQL
Let’s Encrypt SSL/TLS
-------Generally everything working normal  except for the following:
Using SSL (I didn't enable it in admin area because it will kill my cat :(, Anyway SSL is working fine. but the main problem is PAYMENT page looping if SSL Active, while it is working fine without it !
Please check this link(video) below to understand what I mean!
https://u.teknik.io/IskXK.mov
------Another annoying  problem is if I tried to install  plugins or just restart the application it is going to error 502 getaway :( knowing I followed Linux install documentation utterly and repeat it many times. same problem.
Thanks in Advance for any help or tips

Regards /ZAK

Are there any errors in the System Log?  (check the log immediately after you get returned to the cart page)

Thanks for asking.
----For SSL Issue :
There no error there I already cleaned log file to be sure which exact error may  i get but there no even one error!
----For restart application or uploading plugins i get this:
      1-  Error 400. Bad request
      2-  Short message: No access to the news. Website www.nopcommerce.com is not available.

System.Threading.Tasks.TaskCanceledException: The request was canceled due to the configured HttpClient.Timeout of 5 seconds elapsing.
---> System.TimeoutException: A task was canceled.
---> System.Threading.Tasks.TaskCanceledException: A task was canceled.
   at System.Threading.Tasks.TaskCompletionSourceWithCancellation`1.WaitWithCancellationAsync(CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.GetHttp11ConnectionAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.SendWithVersionDetectionAndRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.DiagnosticsHandler.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at Microsoft.Extensions.Http.Logging.LoggingHttpMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at Microsoft.Extensions.Http.Logging.LoggingScopeHttpMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.GetStreamAsyncCore(HttpRequestMessage request, CancellationToken cancellationToken)
   --- End of inner exception stack trace ---
   --- End of inner exception stack trace ---
   at System.Net.Http.HttpClient.HandleFailure(Exception e, Boolean telemetryStarted, HttpResponseMessage response, CancellationTokenSource cts, CancellationToken cancellationToken, CancellationTokenSource pendingRequestsCts)
   at System.Net.Http.HttpClient.GetStreamAsyncCore(HttpRequestMessage request, CancellationToken cancellationToken)
   at Nop.Services.Common.NopHttpClient.GetNewsRssAsync()
   at Nop.Web.Areas.Admin.Factories.HomeModelFactory.<PrepareNopCommerceNewsModelAsync>b__10_0()
   at Nop.Core.Caching.MemoryCacheManager.GetAsync[T](CacheKey key, Func`1 acquire)
   at Nop.Web.Areas.Admin.Factories.HomeModelFactory.PrepareNopCommerceNewsModelAsync()

RE: "Website www.nopcommerce.com is not available."
That's happening on the admin dashboard trying access nopcommerce.com site.  Maybe you have firewall problem.

Already I had disable firewall previously, there is no effect. Keep crashing with 502 error when restarting app.

NO one has any idea about this issue!!