I'm having an issued, on my MR33 I can get v4 IP from DHCP on vlan1 (Native) and dashboard say DHCP error on vlan1 and my cell phone say could not get IP and then no connection i have 98% Free address and I reboot more then one time too. Firmware 25.9.
If you unplug the access point and plug your notebook into the same cable does your machine get an IP address and can it access the Internet?
A screenshot of that AP with the error in dashboard may also help us give you some advice. But @PhilipDAth suggestion is a good place to start.
If you click on the values in the Failures columns, you can see which devices caused the problem.
Some phones don't handle the splash screen properly so guests may fail to click through (which causes an apparent failure). Other failures can occur when a device is in a marginal location. I found it happened when testing and if the mobile device did not keep up with the AP.
Hopefully, as this feature becomes mainstream, it will filter out the false positives.
If you click on the value showing under DHCP failures (5/5), the panel showing the details of the failures will drop down.
In the above case, all the DHCP failures are caused by devices attempting to access the Guest network who do not click the splash through (just legal disclaimer). Depending on the device they are treated as either an untagged DHCP failure or a guest VLAN DHCP failure. They are not actual failures.
The error you get at the top left refers to a problem with the DNS configured on the MR33, so it's related to its LAN configuration.
The DNS failure you have highlighted refers instead to the clients.
As you are experiencing problems on both, I would consider investigating the DNS first, make sure it's reachable and the DNS service is running.