Hello, and welcome.
I'm sorry you're experiencing a problem with your safe.
Do you know the model number? It should be on a sticker near the upper door hinge, along with the serial number (a longer number).
Are you 100% positive of your combination?
Does your safe also require a key to open, along with the combination? If so, is the key round and hollow or does it have 'teeth?'
What type of batteries have you used to replace the old ones?
Thanks for all your additional information, and after you reply, please allow me some time to compose and send your detailed answer.