Sounds light a dead battery. If that isn’t the problem you need to give us a lot more info before we can help you. We’re not psychic due to COVID. If you post back please include answers to all questions.
1. What is the units model and serial numbers.
2. Did this happen all of a sudden?
3. What have you done to remedy the problem?
4. Are you mechanically inclined and have some electrical testing tools?
You must paint us the best picture you can of what is happening, as we are not standing next to you with a strong drink in hand, to see what you see.