@jvkolyad 

I believe the default DHCP pool for the router is 192.168.0.100~199. Make an address reservation under or over that range.

Also if you are doing an address reservation for the printer, make sure the printer itself is set for DHCP and not static for its own network configuration.

@Tony Just got a chance to try it out again today, but I'm having the same issue even when I use an address below or above the address pool (I tried 192.168.0.210 and 192.168.0.90). Both anyone who connects and anyone connected for longer than 2 hours isn't able to obtain an ip address automatically. I've tried restarting the router multiple times, but it didn't change anything.

@Tony I tried 192.168.0.11 and it worked, but I have no clue why

Has there been any progress on this issue? I am having the same problem. As soon as I add an entry to the DHCP address reservation list, the DHCP server becomes unusable and clients on the network are not able to obtain an IP address.

One thing to note... this only started happening when I disabled the WLAN on the router. Previously, when the wireless network was enabled, IP reservations worked fine. I recently set up a separate wireless access point and disabled the wireless radio on the router. After I did that the DHCP server on the router stopped worked. I had to reset the router to get it to work again. As soon as I added the IP reservations back in, it stopped working.

And, yes, the DHCP server on the AP is disabled. The DHCP server on the router is the only one active on the network.

Just following up. I found a workaround from this thread: https://community.tp-link.com/en/home/forum/topic/85863

The issue seems to happen when you have special characters (including spaces) in the description field of the IP reservation entry. If you avoid special characters it seems to work again. This is why it stopped working when I added the access point.. I created a reservation for the AP and the description had a space in it.