After installing the proprietary Nvidia 430.14 drivers on my Ubuntu 18.04 LTS installation, my monitor would have no signal after waking from sleep. Everything else was fine except for this. The solution was to rerun

sudo update-initramfs -u

Before running the above, I also blacklisted nouveau by putting the following lines in /etc/modprobe.d/blacklist.conf

blacklist nouveau
blacklist lbm-nouveau
options nouveau modeset=0
alias nouveau off
alias lbm-nouveau off