Watch will not power on or display

Hello, i have a galaxy watch 4 classic that was left unattended for a while and i tried to charge it but getting no display, i've already tried holding down the buttons, for a while and nothing. left it on a charge for a full 24 hours and nothing. i am techy enough to take the watch apart and got access to the battery, i've measured the voltage at the battery pads and get 4.7v dc. i am assuming that the battery is good, only thing left would be a faulty motherboard. if that's the case i see fully working similar items online selling for about 80 dollars, lowest price for a board i found was a damaged working watch for 59 dollars. just wanted to get feedback to see if i'm on the right track. thank you!