As the Ubuntu installation likely uses ubuntu-drivers autoinstall the problem for you may be that it simply doesn't do it's job properly...
In that case; installing one of the nvidia drivers from the GUI:
Hit the Win/Super-key and type Drivers
a greenish icon will appear saying Additional drivers, click on it.
You will see a selection of nvidia driver versions. Click on one of them. Reboot: Did it work? If not try another one, I'm assuming there is more than one.
If there is no list? Chose the /Ubuntu software\ tab and make sure you have all but Source selected. Then go back to /Additional drivers\
Doing the same from the Recovery console (Text mode):
Reboot,
Hit ESC once as the "BIOS" text appears.
You should end up with the grub menu,
select the Advanced options alternative with the cursor keys, hit Enter
Select the topmost Recovery mode - It will bring up another menu.
Select the fsck, networking and then root shell options in that sequence.
The root shell will appear after yet another Enter;
you're now logged in as root (administrator) in a Bash shell.
Here make sure that there is no broken or half installed nvidia drivers;
simply do apt purge packagename on them.
Then install another one with apt install packagename.
To display a list of INSTALLED nvidia related packages:
$ dpkg --list | grep -E ^ii.*nvidia
To display ALL nvidia-packages, remove -E ^ii.* from the above.
