Hello, what's the model number of your router?

I think you should contact tplink support by email for help.

When blocking a client, you need to go to Advanced - Security - Access Control to unblock it in web interface. The problem that the device name can't synchronize indeed exists.

How many wireless clients do you have? How did you test their speed? Them please go to Advanced-Wireless-Statistics, then check which band and how fast your online wireless clients connecting to.

You mean when you disable NAT boost you can't login anymore? When this problem happened, did your device connected to the router get IP addresses correctly？ Could you ping the gateway?

Have you ever tried to clear your the cache of your browser? What about LEDs, did they work normally or not?