I also found this post some days ago, and after enabling the three services suspend worked on my laptop. However, very recently suspend stops working again on my laptop. When I tried to rerun the commands to enable the three services I got the following prompt:
Failed to enable unit: Unit file nvidia-suspend.service does not exist.
(This is the prompt for nvidia-suspend and it is the same for the other two services.) Also, when I tried to suspend I actually logged out of my account, which did not happen before. Does anyone have any idea about why this happens and how I can resolve the new problem?
Edit: this turns out to be a silly problem… I found that if a service is enabled you cannot enable it again, and after disabling the service and using the workaround in this post suspend now works!