I am currently trying to create a Web Map using content that has been published to my ArcGIS Server as layers. When I first tried to 'Add Layer from Web' to the Web Map in ArcGIS Online, I got an error that said, "Error: Unable to establish a secure connection to the layer. The layer, [layername], cannot be added to the map." I looked through some help documentation that said that my organizational account had settings that specified that layers could only be added using 'https'. It turned out that I had actually been trying to add the layer using 'http' in stead of 'https'. However, upon changing the URL to include https instead of http, I got a generic error that just said, "The layer, [layername], cannot be added to the map". If anyone could point me in the right direction for my next step to troubleshoot this, that would be great. I appreciate your time.
Sorry for the late reply. I have not been logged on in a while. One of my colleagues ended up resolving the problem with someone from ESRI. I believe it had something to do with a security setting on our ArcGIS Server, but I am not entirely sure. Thanks.