does your printer still work with the Windows 10 through direct connection after the update? Tried reset the PS310U but if only the windows 10 doesn't work, check the settings on the computer.

You can turn off the router WiFi. The powerline adapter plugged in the router, will send data to the other adapter/extender, and internet works that way. The extender will generate its own WiFi

It seems the Archer series is a higher level compared to model begins with TL/TD. Usually there is AC number for each model, for example MR200 is AC750, that indicates the maximum wireless link...

Maybe the one you want to upgrade does not fit your router. What's the original firmware version and which one you want to upgrade to?

all your clients connected to the MR3020 have the same issue? if those sites are important to you, contact the tplink support to get some advice

Hard reset the product. Check what's shown on the screen.