If we use two different routers in the same network while both are running in the default router mode then we can access the setup page or setup interface from browser just by IP. But when we use one of the routers as a repeater then we can only enter the setup page of the router which is running in router mode. Why the router setup page cannot be accessed when using the router as repeater? Now how can we change the settings of the router in repeater mode? The only way is to reset router with the hardware key.
Some routers allow you to access them while being in repeater mode. However, if you used the same IP for both that will not work. Others however simply repeat everything and turn off any configuration possibility. This is usually the case with No-Name-Devices. Simply reset the repeater, if possible give the device a unique IP OUTSIDE YOUR NETWORK and then you should be able to access it by changing your computers IP.
Your home network looks like: 192.168.0.0/24 and you set your repeaters IP to 172.16.0.100.
Take an example that you have 2 routers with IPs of 192.168.0.1 (router A) and 192.168.1.1 (router B). You configure router A to be a repeater for router B (which connects to the internet and has the DHCP server).
Now in Universal Repeater mode the router just acts as a bridge that relays packets between the 2 network segments. Because the bridge doesn't need to send/receive anything for its own, it generally doesn't need/have an IP in that same subnet with the DHCP (192.168.1.0). You can check this in the DHCP leased list and you won't see the router A there. But router A still has the old IP and still responds to it. It's just that router B doesn't know about the existence of router A, hence it can't route packets to router A even if you use the correct IP address (192.168.0.1) and will just discard the packets.
You need to set your IP address to static in the same range of router A, e.g. 192.168.0.2 and now you can access it
You can find some info in these questions