@ShellyB615
Thank you for posting on the HP Support Community.
If it's a physical issue with power on button then the All in one computer needs to be serviced,
And, If the computer does not go into sleep mode, does not wake up from sleep mode, or wakes up from sleep mode unexpectedly. Try the below steps
Step 1: Restart the computer
Restarting your computer erases all information in the computer memory, which might restore functionality.
If the issue persists after restarting the computer, continue to the next step.
Step 2: Enable the keyboard to wake the computer
Enabling your keyboard to wake your computer from sleep mode might resolve the issue.
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In Windows, search for and open the Device Manager.
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Click the arrow next to Keyboards, and then double-click the name of your keyboard.

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Click the Power management tab.
If the Power Management tab is not available, click the Change Settings button. The same Keyboard Properties window opens with the Power Management tab available.
If you are prompted for an Administrator password or confirmation, type the password or provide confirmation.
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Select the box next to Allow this device to wake the computer.

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Click OK.
Hope this helps! Keep me posted for further assistance.
Please click “Accept as Solution” if you feel my post solved your issue, it will help others find the solution.
ECHO_LAKE
I am an HP Employee