Hello ewey. Welcome to the HP Forums. I understand your computer will not power on. This is usually due to a hardware failure, but a software failure is also possible. To troubleshoot the issue, please apply the steps in this HP document: Computer does not Start
The troubleshooting steps will help you identify and resolve the issue. If the issue is not resolved, though, you will have to contact HP Phone Support. This is because the computer would be experiencing a hardware failure. You can utilize this website to learn how to contact HP appropriately, based on your region: Contact HP Worldwide
Please let me know if you have any other questions or concerns. Have a great day!
Mario