2400856 - 403 Access denied Error

Trying to access ICM/SAP Web Dispatcher results in the error page.

1.  If icm/HTTP/error_templ_path is not set, you will see "403 Access denied" like below:

2.-  If icm/HTTP/error_templ_path is set, the customized error page will be displayed. 
      The image below shows a default error page (ICMERR-EDEFAULT.html), even if you defined and specific page for ICMERR-EDEFAULT page in /usr/sap/<system id>/<instance nr>/data/icmandir/error_templ

"Our service is not available at the moment. Please try again later. "

Then, checking the dev_icm or dev_webdisp trace. It says:

<level 1 trace>

[Thr 15688] *** ERROR => Permission denied: request not on secure protocol {0000000b} [http_auth.c 1470]

<level 2 trace>

1 ->icm/HTTP/error_templ_path is not set:

[Thr  <nr>] HttpAuthHandler: permission denied: request not on secure protocol
[Thr <nr>] *** ERROR => Permission denied: request not on secure protocol {00000007} [http_auth.c 1470]
[Thr <nr>] HttpPlugInWriteErrorText: check for error templates in "C:\SapWorkDir\exe\sapwebdisp\data\icmandir/error_templ"
[Thr <nr>] HttpPlugInWriteErrorText: return static error for "Permission denied" (-13)
[Thr <nr>] HttpPlugInWriteErrorText: templ_path: C:\SapWorkDir\exe\sapwebdisp\data\icmandir/error_templ, err_idx: -1

2 ->icm/HTTP/error_templ_path is set:

[Thr <nr>] HttpAuthHandler: permission denied: request not on secure protocol
[Thr <nr>] *** ERROR => Permission denied: request not on secure protocol {00051f35} [http_auth.c 1470]
[Thr <nr>] HttpPlugInWriteErrorText: return content of file "C:\SapWorkDir\exe\sapwebdisp\data\icmandir\error_templ\ICMER-EDEFAULT.html" for error: "Permission denied" (-13) 

or 

[Thr <nr>] HttpFileAccessHandler: access file/dir: /usr/sap/<system id>/<instance nr>/<url>
[Thr <nr>] HttpPlugInWriteErrorText: return static error for "Permission denied" (-13)
[Thr <nr>] HttpPlugInWriteErrorText: templ_path: /usr/sap/<system id>/data/icmandir/error_templ, err_idx: -1

Another possible message in the trace is:

[Thr 139897064650496] *** ERROR => permission denied for [URL path] : request not on secure protocol {000a148a} [http_route.c 3507]
[Thr 139897064650496]              <Web Dispatcher IP and port/URL path>
[Thr 139897064650496]              role: Server, protocol: HTTP, local: [Web Dispatcher IP and port], peer: [client IP and port]

• ICM or SAP Web Dispatcher. The parameter icm/HTTP/auth_<XX> is activated.

Permission denied, request not on secure protocol, icm/HTTP/auth PERMFILE, ICMERR-EDEFAULT, error_templ , KBA , BC-CST-IC , Internet Communication Manager , BC-CST-WDP , Web Dispatcher , Problem