3 long beeps followed 4 short beeps

[ProPCTech]

For anyone having issues with  3 long + 4 short beeps on any All-in-One, try reseating the AC adapter into the desktop  OR  replacing the 150W adapter.  FYI, I personally had this problem with a customer product return with a missing adapter & I initially used a 90W adapter that fits and it STILL had the beeping issue.  I looked up what the original OEM adapter and discovered it uses a 150W adapter.  There was not enough power to boot the system.

[Echo_Lake]

@ProPCTech
Thank you for posting on HP Support Community.

Don't worry as I'll be glad to help, I have a few troubleshooting steps we could try to fix the issue:  

Before troubleshooting startup issues, remove or disconnect all discs and devices from the computer.

• Step 1: Remove discs and devices
• Step 2: Perform a hard reset
• Step 3: Run hardware diagnostic tests
• Step 4: Refresh or reset your PC. Click here: https://support.hp.com/in-en/document/c04718479 to complete the troubleshooting steps. By the end of the article, you will be able to fix the issue.

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.