If you have access to the installer have you tried creating the bootable thumb drive from here?
Reading closer you don't have access to the installer. Running the online installer won't work because apple pulled the download links that it uses. I suspect this is thinly veiled attempt at pushing people to upgrade.
Check this out: https://diskmakerx.com. ...
The folks who observed "AC power" contributes are on to something.
High chassis temperature from charging together with peripherals plugged in can cause this issue. Simply moving the charging cable from the left to the right ports can be enough to cool the hotspot and resolve the problem. On a machine with MagSafe try unplugging peripherals from the left ...
You can use a file converter online without downloading a new software on your Mac Book or PC . You can find various on Google search. I use Convert zip to rar for free to convert my files.
I hope it works for you too.
It's 2019 and I had a similar problem with mojave : three displays on my remote (work) computer, only one on my client (home) computer.
Many of these solutions that refer to MissionControl will help you swap Desktops, not Displays (physical monitors). Swapping virtual Desktops is easy enough: just add the MissionControl icon to your dock.
To swap displays, ...
I was able to do it by using a rectangular annotation via Tools -> Annotate -> Rectangle. Make sure it covers the signature and just make the background and border match the color of your document background (white in my case).