Ensure your home internet is working properly. Test it with another device.
Turn off your TV, wait for a few minutes, then turn it back on.
Go to 'Settings' > 'Network' > 'Set up connection' on your TCL TV.
If your TV remembers an old network, forget it and reconnect.
Ensure your TV's software is up to date. Go to 'Settings' > 'System' > 'System update'.
If all else fails, perform a factory reset. Remember, this will erase all your settings.