I have my admin running on http://nodered:1880/adminpath/ and I was not able to generate the access token. I ended up copying the URL it was trying to execute, added my adminpath to it, copied the token from the resulting page and then enabled the "Add" button from Chrome console to get everything to save.
After all was said and done, it works flawlessly, but took me a while to figure out what was going on.
I have my admin running on http://nodered:1880/adminpath/ and I was not able to generate the access token. I ended up copying the URL it was trying to execute, added my adminpath to it, copied the token from the resulting page and then enabled the "Add" button from Chrome console to get everything to save.
After all was said and done, it works flawlessly, but took me a while to figure out what was going on.