Windows 10: My Laptop will not sleep. It's an Acer Aspire 5250 Series

The common cause of many PC problems is Norton Security programs. Temporarily disable it completely and use the inbuilt Windows Defender for antivirus and malware protection. You will need to load the most recent definitions updates.

Secondly, check in device manager for any yellow warning triangles against devices. If you find any of these, you may need to get these drivers from Acer from Download Drivers and Manuals | Acer Official Site

You should choose the Windows 8 update for your 64- or 32-bit version of Windows (I would guess 64-bit)
Acer have provided a utility to detect your hardware - click on the line which says:

Need to know the hardware to choose the right drivers on your system? >

- to download the utility.

It is also worth checking if there is a BIOS upgrade available.

Power management features are largely handled by your chipset. You may be using Microsoft generic drivers from your Windows 10 installation which do not utilize these chipset features, and therefore the sleep function is not working as it should.
Acer do not seem to provide these in their driver updates so look to the AMD section here: Latest AMD Chipset Drivers Released - Windows 10 Forums

Also the GPU while you are at it - Should be ATI Radeon? Make sure that is up to date too, and not being driven by a generic driver.

Then hopefully, when you get back to us, you should be able to enable sleep.

 

I hope so. Thanks everyone for your help.

 

Fafhrd, should I still do a BIOS update and install the latest chipset?

 

Well, I thought I had the issue resolved but I guess not. Its not sleeping again.

 

Some older pcs with award bios have a setting where you can choose the different sleep settings. Have a read here Difference between S1 (POS) and S3 (STR) standby mode in BIOS?