I recently purchased a brand new EAP225 to act as an additional AP in my home, to expand coverage to an additional floor. It is wired via ethernet to my switch, and when factory reset it broadcasts the correct tp_link network. 

When I connect to the tp_link network, it does not provide DHCP, so I have to set a manual IP. Not an issue, I know the default network config is 192.168.0.0/24, with the AP at 192.168.0.254. So I set the correct ip and subnet, and it works. I connect to the web UI, and follow the initial instructions. Since I want this to act as an additional AP on an existing network, I put in the same SSID and password as the existing network. It applies these settings and reboots. 

Now I do not know if I am connected to the existing AP or the new once, since the SSID and password are the same. Which should be no issue, I already have 2 other APs that do the same. But what the issue is, is that I cannot access the AP over the IP anymore. My home network is 192.168.1.0/24. Now on my firewall I added a new ip/sub-interface with the 192.168.0.0/24, and gave the new interface IP 192.168.0.1/24. 

From any network connected device, I can ping through the networks to 192.168.0.1, the gateway for that new network I added. But I cannot ping or access 192.168.0.254. Also, when I log on to my firewall to check the ARP to see if it is even on there, I do not see it. I show arp, and there is no entry for the MAC in the arp table of the router. 

48:22:54:38:BC:B8 is the MAC, and here is the entry in the ARP table when I try to ping 192.168.0.254;

index=22 ifname=internal 192.168.0.254 state=00000001 use=99 confirm=6999 update=99 ref=2

Can confirm the routing table has entries for these networks;

tab=254 vf=0 scope=253 type=1 proto=2 prio=0 0.0.0.0/0.0.0.0/0->192.168.0.0/24 pref=192.168.0.1 gwy=0.0.0.0 dev=22(internal)
tab=254 vf=0 scope=253 type=1 proto=2 prio=0 0.0.0.0/0.0.0.0/0->192.168.1.0/24 pref=192.168.1.1 gwy=0.0.0.0 dev=22(internal)

Internal is the interface name. These routes are correct. 

firewall # execute ping 192.168.0.254
PING 192.168.0.254 (192.168.0.254): 56 data bytes

--- 192.168.0.254 ping statistics ---
5 packets transmitted, 0 packets received, 100% packet loss

I am at a loss on what to do here, or how to set this up correctly to be an additional AP on my network. I have tested by forgetting all IP saved networks on my phone, walked to an area where this AP would be by far the strongest AP for the network, connected--and confirmed it provided by IP, DHCP, DNS information. So it did not work. 

Looking for steps to fix this. 

When I join my laptop to the default TP_Link network, I can assign an IP to the correct network and connect over IP, and run the Omada software controller--it shows the device as unknown, and when I try to adopt it, it says failed due to changed password. But this is immediately after a factor reboot via the reset button, and I confirmed via connecting to the web UI interface and logging in with admin/admin that is was correct.

A bit lost on this one, not sure how to get this up and running in my scenario. If I have to create a different SSID, set everything up, and then change the SSID field last and apply to have it mesh with the existing network?