Laird Gateway RG191 is reconnecting every 15 seconds, what might be the issue?

image_2021-11-01_12-14-18

Migration from TTNv2 to TTNv3

Firstly, I updated firmware on Laird RG191, and switch configuration to CUPS Server and LNS server
based on the following LoRa Basics™ Station | The Things Stack for LoRaWAN

Keys are all generated and loaded.
Minimal Certificate is loaded.

I checked, wi-fi is working good.

Any ideas why is happening?