I recently purchased a 65" Class 7 Series Smart TV. Everything was working fine for a day or two and I noticed that every time I would turn of my tv for a long time (one day to another), it would disconnect from Wifi. Googled this, was advised to do a soft reset (press and hold the power button) which successfully auto connects to the wifi but only for that day. The TV disconnects when I turn it off for that day.
I ended up exchanging the TV for a bigger one (75" Class 7 Series LED 4K UHD Smart Tizen TV Model UN75TU7000FXZA SKU: 6401719) because the TV expert from Best Buy said it was "the motherboard." Installed it yesterday, and today it disconnected from wifi. On both TVs, I performed the troubleshooting steps advised on other forums: soft reset, hard reset, reset router, firmware update, manually entered IP address.
PLEASE HELP! This is annoying!
also check that your router isn't limiting the time a device is connected.
I find that my Galaxy S20 Ultra will sometimes lose connection to my WiFi 5Ghz after a couple days, but will stay connected to the 2.4Ghz frequency with no issue.