Hi ArleneH###,
Thank you for reaching out Microsoft Community. We're sorry to know that your Surface device won't turn on anymore.
If you already press and hold the power button and the volume + for 15-20 seconds and your Surface device isn't reacting to it, then the best resolution I can suggest is to either get a replacement for this unit or upgrading it to a new model. The issue could be its motherboard is already defective, though the PSU's tip lights up when it's connected to the charging port but it still won't turn on if the hardware component of the Surface device especially its motherboard is already defective. In this case, there's no other troubleshooting steps that can be performed on a Surface device that is no longer turning on.
If you prefer to get a replacement for this unit, please don't hesitate to contact our**Microsoft Surface Support**for further assistance.
If this answers your question, feel free to mark this post as an answer. Otherwise, don't hesitate to respond to this thread if there's anything else that needs to be addressed.
Kind Regards,
Crest_Z