Thanks very much Robert,
I tried that instead but it didn't help -- I am starting to think the problems are caused by my organization's reverse proxy setup, although I have already tried to account for that and don't know what else to do.
My proxy.config has this:
<serverUrl url="http://<myorg>.maps.arcgis.com"
username="username"
password="password"
matchAll="true"/>
Here are a couple of other pieces of the mystery:
These work fine:
http://<myurl>/<mysite>/proxy/proxy.ashx?ping
http://<myurl>/<mysite>/proxy/proxy.ashx?http://services.arcgisonline.com
This is the url that errors out in my app:
http://<myurl>/<mysite>/proxy/proxy.ashx?http://<myorg>.maps.arcgis.com/sharing/rest/portals/self?f=json&dojo.preventCache=1485363849222&callback=dojo.io.script.jsonp_dojoIoScript1._jsonpCallback
BUT -- this works fine (same as above string without the proxy):
http://<myorg>.maps.arcgis.com/sharing/rest/portals/self?f=json&dojo.preventCache=1485363849222&callback=dojo.io.script.jsonp_dojoIoScript1._jsonpCallback
In my proxy.config I have tried both of these:
http://<myorg>.maps.arcgis.com/sharing/rest
http://<myorg>.maps.arcgis.com
In the reverse proxy config I have:
http://<myorg>.maps.arcgis.com
http://<myurl>/<mysite>/proxy/proxy.ashx
http://<myurl>/<mysite>
I don't know what else to try! Thanks for any ideas. I'm wondering if it is not possible to use Web AppBuilder with a reverse proxy.
proxies