We are having the same issue:
MS IIS Reverse proxy server, two arcgis servers, web server (with web adapter and Portal for arcgis) are all located on the same subnet and DMZ.
We published a print service with templates.
The print service does not work in ESRI web appbuilder the Print widget.
The errors are:
1. A connection with the server could not be established (WinINet Error while using HTTPS security, 12029), URL = https://public-url/arcgis/rest/info?f=json
2. A connection with the server could not be established (WinINet Error while using HTTPS security, 12029), URL = https://public-url/arcgis/rest/services/folder/AClassA/MapServer?f=json
3. Error executing tool. Export Web Map : Layer "AClassA": Unable to connect to map server at https://public-url/arcgis/rest/services/folder/AClassA/MapServer. Failed to execute (ExportWebMap). Failed to execute (Export Web Map).
Could the experts in ESRI Redlands give some insights on the issue and provide possible solutions?
Thanks,
JYI