I had a device trying to connect to our guest SSID that had successfully connected before but wasn't able to connect to the internet until it "forgot" the SSID and then reconnected. I looked in the logs and saw the 802.11 disassociation message was "disassociated due to captive portal security failure". I haven't seen that one before, although looking through the logs shows several of these over the weekend on this network. It sounds like it has to do with the splash page that we have setup on the guest SSID, but I haven't been able to find a description of what that message means. We haven't made any recent changes on the splash page. Most new and returning devices can connect immediately, some returning devices have to forget the SSID and then connect again. If anyone has any thoughts on this message and where I should look I would appreciate it.
The AP showing the majority of those messages is an MR84 but I'm also seeing the message on an MR52 on the same network. Both have up to date firmware.
The spash page is set up as a simple acknowledgement of our network use agreement every 90 days.