Keenetic Ultra LAN blocking?

Question

network hardware

Tell me this question, there is a Keenetic Ultra router and a Keenetic Extra router. There is a local area network about 100 computers. Ultra works well and distributes wifi in the office. I made a repeater on the extra router and, when connected to the local network, it simply blocks its work completely. Tell me what could be the problem?

Answer 1

As an option - a loop in the network, DHCP is not disabled on the 2nd router

Answer 2

Check banal things first of all - who is assigned to whom by the gateway, is there a SP conflict and what happens to routing with both routers turned on

Answer 3

Checked dhcp is disabled