Windows 7 will not enter sleep mode automatically

Source

Please first uninstall all unnecessary devices and see if the issue can be resolved. Also, test inClean Boot as Solution_Provider mentioned. If the issue disappears in the Clean Boot environment, we can use a 50/50 approach to quickly narrow down which entry is causing the issue.

 Besides, please use Powercfg command to check this issue. To do that, refer to the steps below:

1. Click the Start Button, type "cmd" (without quotation marks), right click on the "Cmd.exe" in the search result list and select "Run as administrator".

2. Type "powercfg -devicequery wake_armed" (without quotation marks) in the open window and press Enter Key.

3. A list of the configured devices to wake the computer will be received, then please type the following command to disable them one by one and see if the culprit can be found. (We may test the result after disabling each device.)

Powercfg -devicedisablewake "devicename"

Note: "devicename" is a device name listed as a result of running the first command.

For example, if the network card "Broadcom NetXtreme Gigabit Ethernet" is listed, we can type the following command to disable it and press Enter.

Powercfg -devicedisablewake "Broadcom NetXtreme Gigabit Ethernet"

4. Please repeat the steps for other devices in the list.

5. Reboot the computer and check this issue again.

What's the result now?

For more information, please refer to Powercfg Command-Line Options.

If the issue persists, please refer to the following articles for more troubleshooting suggestions:

Sleep and hibernation: frequently asked questions

Windows 7 does not go to sleep