Do you still see the 5G wireless name? Does this problem happen on all your devices? Make sure the wireless light is on and change the channel of 5G to 36 or 144. By the way, do you see any error...

What's the model number? Normally you can login to the TP-Link page using the login address and usename/password on the bottom label of a TP-Link device. In the configuration menu, find wireless to...

Check the Ethernet port on the router with a computer which is used to connected to the TL-WA901ND. Rese and reconfiguration may help.

TL-WR841N doesn't support https block. However, the IP address and port number can be blocked or replace it with an advanced router.

No much useful information in the description. Normally perform a reset and reconfiguration will help. Or better to contact Vietnam support for help.;)

Disable firewall and anti-virus on the computer, or log in safe mode before you plug the adapter in. If this can't help, you may get another adapter.