leewhatB

Can you pull cable to there?

Else you would need to consider point to point system.

Try access it using mobile data.

Local will work because it is your network. Outside of that depends on ISP.

Does it say any error when trying to access? web browser?

Tried to delete the wifi on iPhone and reconnect again?

It’s useful for local transfer between computer like NAS. You do need to upgrade other equipment to 10G as well.

Did you setup router 2 as Access Point mode and plug the cable from router 1 to LAN port, not WAN port router 2?

4K streaming is around 25Mbps, so x2 = 50Mbps, still doable.

I would connect it to main router first, in case something happen to MR2200AC, wired device still have internet.

Do your phone/laptop support Wifi 6? For higher max speed, you will need to use higher bandwidth like 80Mhz or 160MHz, assuming your device support and not much interference.

Can you check if this turned on? https://support.norton.com/sp/en/us/home/current/solutions/v138204009

Disable the DHCP on cAP AX?