I would certainly be pointing my finger at the proxy in some way. I have seen proxies do all sorts of fun things with these ArcGIS online connections.
Do you have your workbench setup to use the assigned proxy?
In FME Workbench can you go to tools…FME
Options…network proxy and just check "Use system proxy settings" is checked.
Can your IT let you get external without the proxy or find a way of using FME outside of your network? If you can prove it works from somewhere else, then you know its the proxy or is something else.
Hi @londonhb185,
In addition to the suggestion from @todd_davis, you could take a close look at the token generated - I've had success troubleshooting in this way using a token in the ArcGIS Server Feature Service Reader. Perhaps the Portal Reader is similar:
From what service (REST API or otherwise) did you generate the token? Did you generate it in the browser and then copy-paste to FME? Is it bound to an IP address or HTTP Referer that would not synchronize with use in FME Desktop? Has it expired? Have you tried the token in the ArcGIS Server Feature Service Reader instead?
Hope this helps.
Nathan