How about configure the C9 as access point?

Did you reset the router? I would suggest you change the 5GHz settings on the router, like choose the least used channel. If problem happens frequently, contact tplink support

make sure the format of the file you upload is .bin

Did you get in contact with TP-Link support recently?

Hi guys, thanks for the info. My Android Phone(Huaiwei ) seems to be working fine with Deco system. How about your other devices?

What's the hardware and firmware version of your router? You can't copy the settings on the router and paste into somewhere else, or the opposite? Maybe reboot or reset the router to see what happen,...