Zyxel EX5601-T1 - connection of smart devices

cw3l

Hi, I've recently received the router Zyxel EX5601-T1 from my ISP. An issue I've spotted right off the bat, is that i could not connect any smart devices to it (i.e. yeelight light bulbs). I was trying to do it on the 2.4Ghz network, 20Mhz, channel set manually to 1, with no success. On my old router, with the default configuration the light bulbs connected without any issues. Is there anything obvious that i'm missing in the settings of the Zyxel that blocks the connection? Thanks in advance.