I’ve been running HippoCMS locally for over a year, and we have it in various server environments, including production, too. Currently on 12.3.0. Suddenly, possibly because of something I have changed but cannot identity and fix, I’ve been unable to view any of my channels in the Channel Manager locally. On the server it is working as expected. I’m hoping this is an obvious mistake on my side that someone is able to point out.
All my channels are listed correctly, but selecting any of them displays a “Forbidden” page, as well as momentarily popping up two messages in the top right corner, “Failed to enter Edit mode” and “Failed to retrieve the sitemap for the current channel”
The log shows two warnings that could be of value:
[INFO] [talledLocalContainer] 04.06.2019 06:25:21 WARN http-nio-8080-exec-2 [CmsSecurityValve.invoke:112] Invalid request to redirect for authentication because request method is 'POST' and only 'GET' or 'HEAD' are allowed [INFO] [talledLocalContainer] 04.06.2019 06:25:22 WARN http-nio-8080-exec-8 [AbstractConfigResource.logAndReturnServerError:183] java.lang.IllegalStateException: Could not find rendering mount id on request session.
I see two failed network requests in my browser while trying to access a channel:
The browser console displays many errors, mostly related to values being ‘undefined’ after the failed network requests.
I’m logged in with the default admin user (admin:everywhere, readwrite:defaultwrite, editor:hippodocuments). Other more restricted users give the same result.
I have searched this site and Google for these messages, but found no result. While none of the issues seemed exactly the same I also tried many of the solutions on the Channel Manager Troubleshooting  page.
“Could not find rendering mount id on request session.” seems to be the most relevant issue, but I have no idea what is causing it or how to fix it.
Does anyone have any idea what is going on here? Any more info I can provide that’ll help?