Ubuntu 18.04 only booting in recovery mode

[foxnerdaysmoo]

I recently got a new Dell Precision 3431 with a Quadro P620 NVIDIA Graphics card. I am running Ubuntu 18.04, with nvidia-driver-455 (in additional drivers app).
After reading through threads of similar problems, I have made sure my graphics drivers are up to date.
I ran

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

And selected the most recent driver in Additional Drivers; it didn't work.
If I boot normally, a flashing cursor would appear. If I press keys they will appear, then get removed.

sudo lswh
*-display UNCLAIMED
description: VGA compatible controller
product: GP107GL [Quadro P620]
vendor: NVIDIA Corporation
physical id: 0
bus info: pci@0000:01:00.0
version: a1
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress vga_controller cap_list
configuration: latency=0
resources: memory:a3000000-a3ffffff memory:90000000-9fffffff memory:a0000000-a1ffffff ioport:3000(size=128) memory:c0000-dffff

*-display UNCLAIMED
description: Display controller
product: UHD Graphics 630 (Desktop)
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pciexpress msi pm cap_list
configuration: latency=0
resources: memory:a2000000-a2ffffff memory:80000000-8fffffff ioport:4000(size=64)

[CelticWarrior]

Welcome.

Quadro P620 needs 450.xx,, not the latest version.

[foxnerdaysmoo]

Thank you! After switching from 455 to 450, it works perfectly!