I have a 2014 Nissan Altima that the key fob does not work to unlock and lock the doors it will turn on the ignition but there is no key cylinder to plug in the key and do what I understand is the normal restart how do you restart it or reset the key fob if there is no ignition key slot

Not sure if I understand your question. Worse case scenario, you can have the dealership reprogram your key FOB if it's not able to control all of its standard features. Or your can try googling the key FOBs reprogramming protocol.

is it an OE key fob or aftermarket fob? If it's OE, take it to the dealer. If not, try contacting the manufacturer of the key fob for programming instructions.

Did the lock and unlock buttons ever work?

If they did work at some point:
Try disconnecting the vehicle battery (both positive and negative terminals) for at least 10 minutes. This will give it a chance to reset

If they never worked:
You will most likely have to get it programmed. I recommend a locksmith over the dealer, they will be a little less costly. It is usually less expensive to get 2 programmed at the same time, so if you have more than one to program now is the time to do it. You can order spares from this site https://keylessentryremotefob.com