I am not sure what could have gone wrong here.
But if I am to troubleshoot such an iPad, I'd start first by resetting the iPad: unscrew the board, wedge a plastic card underneath the logic board next to the the battery connector, and lift slightly to make the battery disconnect. Re-screw everything, disconnect the charging dock, clean the connector on the board, reseat the charging dock, and leave the iPad to charge for 20 minutes, and see if it gets back to life.
This way I would have reset the iPad and ruled out a loose charging dock.
If reseating the charging dock does not help, I disconnect the PMV (Power-Mute-Volume control cable) from the board and try again (start the iPad by connecting it to a charger).
Then I'd try a new charging dock.
If that still doesn't help, I examine the apparent parts of the board, looking for pry damage such as broken components, part or completely torn off the board.
If the iPad restarts normally at some point, but still doesn't respond to the Power Button being pressed, then it could be that you tore the PMV cable when separating the glass. Examine it carefully. It has 2 parts that run through the aluminum frame on the top right corner. Are they part or completely torn, or some piece missing?
These are speculations, but you have to start somewhere, and this is assuming that the iPad had only a broken glass, no liquid damage, and worked perfectly before the attempted repair. If not, let us know its history.