While you can try cleaning all contacts the advice is that given the age of MiniDV camcorders and how much it can run to repair if you find a repair center is to only worry about it if there is content to extract.
For that you hit Ebay and see if you can buy a working one then get the content out and sell the entire lot and never look back.
I have an older JVC Camcorder that won't power up using battery or ac charger and I know the battery is good and I also volt tested the adapter to make sure it's getting juice so the issue is in the camera itself. Is there any advice on repairs? It worked fine two or three years ago.... if that helps when it was last used.