@alcrun8 could be a bad battery so I would change it once more. If that still does not help you want to check your charger, your charging cable as well as the charging port. Make sure that there are no broken, bend or corroded pins and that there is no debris in that. Use a few puffs of compressed air to clean it. Anything after that will require you to disassemble your phone and check the components on the board etc. Problem with that is that ZTE does not offer their schematics to service manuals to the public. So you may have to find someone that specialized on ZTE phone board repair.