Due to the liquid damage, before anything else, I’d advise you to inspect the charging port for corrosion and see what it pulls from an amp meter. If it pulls 0.00 A @ 0V, it isn’t worth repairing. If If it pulls 0.00 A @ ~5V, the charging port is the issue. If it pulls between 0.07-0.09 A @ ~5V, it is most likely board damage (losing current btw the charging port and the battery). If it pulls between 0.12-0.20 A @ ~5V, the battery is bad.
After that, I would recommend either opening it yourself to take a look at the inside and look for corrosion on the board, or take it to a repair shop and let them take a look at it to see if there is damage to the board. In the event that the board is damaged, I would consider the device beyond economical repair.