Can’t REconnect to router after device disconnects

Modem is a TP-Link TD-8817
Wireless router is a TP-Link TL-WR720N

Both have done the quick setup, it seems everything works fine until a device tries to connect to the network for a second time. For example, sleeping a computer or leaving and coming home with a cellphone.

The device can see the network, but it can’t connect. Restarting the wireless router then lets the device connect. This happens on numerous devices around the house.

Haven’t found any similar thread online and have been looking a lot. Any help (or even just an idea of how to phrase this problem in google) is very welcome.