seems your 902ac fail to connect to wifi router, try config 20MHz, 11ac/n mixed, channel 36, no encryption on the wifi router may help

as the cameras have fixed IP, you need configure gateway192.168.1.1 to them as well, otherwise they could only be access on your local network, but not remote network and the internal port shall be...

this router don't support ssl, so I cannot find a public mail server such as gmail, outlook to apply on this settings

Good feature for Restaurant and Cafe

you can reset it to factory settings by pressing the reset button for about 5 sec

choose the hardware version in this link, and you will find it https://www.tp-link.com/en/download/TL-WR840N.html#Firmware