This is a little trick that comes in VERY handy at times, like when something doesn’t work. Try with a Soft Reset, and pretty often it does fix whatever the needed to be fixed.
If you got a phone where you can remove the battery, turn it simply off and remove the battery. That’s IT! Do not remove the battery while phone is ON (unless you have to) since that can (if you’re very very unlucky damage the phone). Just turn it off, and remove the battery.
If you got a One series phone, you just keep the power button pressed for around 10 seconds. After 6-7 seconds you get a prompt to keep it pressed to restart. Just as simple as that!