Ok, so I have this very strange problem. I have a Synolgy NAS running DSM 7.0.1-42218 Update 2. The version of Firefox is 97.0.1 (64-bit). Everything worked just fine until I changed the ip-adress for the appliance and moved it to another IP-subnett. After the adress change, I can load the Web UI logon page, and I can submit the username and password, but then the page just hangs without any response. I have tried different things to troubleshoot this. 1) First of all; The fact that the logon page itself actually loads ... rules out issues with routing and fw issues. I can also log into the same NAS device with SSH, so routing and/or fw-rules is not an issue. 2) I have tested with two other browsers (Edge and Chrome) which both let me log in to the page without any problems. This tells me this seems to be an browser related issue. 3) I have disabled two addons for the site privacy badger and addblock plus, just to make sure those are not interfering with anything 4) I have deleted the cache and tried again, with no success 5) I have started another instance of Firefox (portable from www.portableapps.com), without that solving anything 6) On the Synology device I have checked the option "Clear all saved user login sessions upon system restart" under security What I can not understand is that this worked with the same browser version before that IP-change, but for some strange reason is not working now. The setup of the NAS itself is pretty straight forward. The most "fancy" setting is that I have configured a link aggregation for all the NICs on the appliance, but I can't see how this should be relevant in this context. Especially since everything seems to work, just not from Firefox. Any input on this would be appreciated very much. Cheers