Computer goes into sleep mode, but won't wake up

Install the intel Microcode Package for your MB/CPU

Looks like you have an Intel board and might want the microcode for it:

 sudo apt install intel-microdcode

Next, make sure you have the latest Video Drivers

Updated graphics drivers, when using NVIDIA cards, will fix many problems, and so it is a good place to start. I see you are using the open source "nouveau" driver, so we will start with updating that. First add the PPA to provide latest drivers:

sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt update
sudo apt upgrade

Now reboot and see if it works for you. If so, you are done! If not, try using the PRO drivers:

Install NVIDIA Pro Drivers (Optional)

If the latest neoveau drivers don't work, you can try the pro drivers instead. There are two options, 390 and 396. The 396 breaks my system, so I will give instructions on how to install 390 as well as how to try the 396 (and fix if needed).

To install the 390 driver:

sudo apt install nvidia-driver-390

And then reboot to test your system... if it works you can either stick with that or try the 396 diver:

sudo apt install nvidia-driver-396

And reboot... if this driver prevents X from starting, switch to a new TTY with "Ctrl+Alt+F3", log in and do the following:

sudo apt purge nvidia-driver-*
sudo apt autoremove && sudo apt autoclean
sudo apt install nvidia-driver-390
sudo reboot

If you have nvidia graphics card, this problem can be solved easily. Just change GRUB_CMDLINE_LINUX="" to GRUB_CMDLINE_LINUX="nouveau.modeset=0" in /etc/default/grub file then sudo update-grub && reboot. Also check in app store, you might need to install additional drivers.

If still doesn't solves the problem try this cat /sys/power/mem_sleep. If it does not print s2idle [deep] then check this for solving.

for those who don't have nvidia graphics, bad luck guys. As of 2021 it still not solved. The only way to solve the issue is downgrading kernel to 4.14.0-041400-generic which will solve the problem of hanging when lid closed.

Note: I said lid closed because this version doesn't enter suspend mode when lid closed but some how manages to turn off screen & backlight. :) This is the version I am currently using.

You can downgrade kernel by using ukuu tool or by manually compiling source. For ukuu tool you need to pay money but if you dont want to pay check github releases section & download it from there.

There a issue page that still not closed but I didnt see any reply from devs in 2021.

Some bug detailed information can be found here & here.

My system specs: (lscpu)

Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
CPU(s):              4
On-line CPU(s) list: 0-3
Thread(s) per core:  1
Core(s) per socket:  4
Socket(s):           1
NUMA node(s):        1
Vendor ID:           GenuineIntel
CPU family:          6
Model:               55
Model name:          Intel(R) Pentium(R) CPU  N3510  @ 1.99GHz