Good news! It's powering on with a different board. Unfortunately it doesn't seem to have OS installed, but it is powering on with the new board with access to boot menu and BIOS settings.

Does the battery from a non-working TPT2 get charged if installed in your working TPT2?
Even though this is not exactly root-causing, I strongly suspect it is the PMIC. If you have the means, replace the PMIC.