@Phansn look at this forum post ... How to recovery the router when you bricked it? https://community.tp-link.com/en/home/forum/topic/81462

u can try go back to the previous firmware, also u can try vary the 5g wifi channel setting and protocol try just ac, than without etc, could be around using the same channel creating lot of...

you can also use WDS settings by setting one as main router and the second as a slave

Hi, if anyone has an old firmware from 2018 for the Archer C7 V5, i would highly appreciate. THX.