Domestic safes with electronic keypads will use batteries. These will not last forever. If they go flat or leak the safe will not open. In that case you will either have to use the backup key or battery backup facility, depending on your own particular safe.
If you’ve lost your back up keys, you may need a locksmith to open the safe for you. Check you know where the keys are, and change batteries when the keypad tells you to change them.
We were called to open an electronic safe with these batteries fitted. The override keys had been lost. Can you see anything wrong?