Cannot enable printer in Printers pane

## Prerequisites
- [X] I have searched open and closed issues for duplicates.

## Describe the bug
Enabling a printer by toggling its switch to the "on" position does not seem to make the printer functional. Additionally, after relaunching System Settings, the toggle has moved itself back to the "off" position.

### To Reproduce
Steps to reproduce the behavior:
1. Launch System Settings.

I see all 3 printers on my LAN here, as expected. All are marked "Disabled".

2. Click on the printer I want to enable
3. Click on the large toggle button in the upper right of the pane to set it to the "on" position

At this point, the word "Disabled" still appears below the printer in the list of printers.

4. Quit System Settings via the window close widget
5. Launch System Settings again

Printer is still marked "Disabled"

6. Select the same printer again

Toggle switch has reset itself to "off" position.

### Expected behavior

- Printer reads "enabled" after being toggled on
- Printer is usable from applications which can print
- Printer toggle switch does not revert to "off" position on subsequence launches of System Settings

### Screenshots or screen recordings

Will provide if desired.

### Logs

Happy to provide, but I'm new to the OS and not sure which logs are relevant or where they're located. Let me know!

## Platform Information

elementary OS 5.0 Juno
Built on Ubuntu 18.04.2 LTS
Linux 4.15.0-66-generic
GTK 3.22.30

Dual-core Intel i7-6560U @ 2.250 GHz
Iris Graphics 540
8 GB Memory
981.1 GB Storage

- [ ] I'm using the latest version from git that I've manually compiled
- [X] I'm using the latest released stable version

## Additional context

Printer in question is HP LaserJet M402dw.

---
Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/83037802-cannot-enable-printer-in-printers-pane?utm_campaign=plugin&utm_content=tracker%2F60188248&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F60188248&utm_medium=issues&utm_source=github).