@Judge Good evening. Sorry to hear about your daughter’s problem with Pencil2D. In this case it seems the power surge interrupted the saving procedure which prevented essential files to be written into the project. It is also possible that some of the work was lost as well so hopefully you can ready your daughter for that.
That said, If possible send us the project file (the one that can’t be opened) so we can try to recover whatever was left inside for you and we’ll send a new file that has such contents.
You can use google drive, dropbox, mega.nz or wetransfer.com to send us a link to the file and I’ll gladly track this issue so we can have this processed as soon as possible.
For future problems with this you can also consider following this guide which outlines prevention tips to avoid losing work and shares some of the steps we sometimes take to recover lost work in different capacities:
Also if you are using a Windows 10 operating system, please consider looking into this guide to avoid permissions problems while using Pencil2D