RT-AC66U not resolving local names

[MrPeach2]

I have had this router for forever, and it has never had this issue before. I recently updated the router to the latest firmware (3.0.0.4.382_52287) reset to factory settings, then put in all my configuration stuff (fixed IP allocations/names/DHCP range, etc). Same damn thing I've been doing every damn time I update this thing. However, my port forwards aren't working and neither are my local host names.

I have been banging my head against this for the last two hours and made no progress whatsoever.

Help?