I bought an app called Palua on the App Store a few years ago. Now I have a new personal Mac and I believe the app is no longer on the store. I know that it works on the latest version of macOS since I still use it on my work Mac. Is there a way for me to install it again, since I did indeed pay for it? I do not see it in my 'Purchased' apps in the App Store, which is where I hoped to find it.
Apps on the App Store (iOS, tvOS) and on the Mac App Store cannot be re-downloaded if
- the developer removes the app
- Apple removes the app for various reasons (e.g. violation of App Store policies, copyright infringements)
Since 2015 Apple removes apps from your purchase history as well. A well-known example is "Monkey Island 2" by Disney. It was removed with no option to re-download a copy of the game.
Try to contact the developer of the app. Maybe he/she can send you a copy of the app.
Actually, there may be another couple of ways for you to install the app in question. These are not definitive solutions as the success you have will depend on the specific apps in question.
Firstly, you may be able to re-install it if you have Time Machine backups that contain the app. If so, you should be able to use that (especially since you're saying it still works in macOS Sierra).
The second option is that you may be able to use the version from your work Mac, depending on what account it was downloaded under and whether or not you're able to use that account. Essentially you'd just copy the app from the work Mac to your personal Mac and try running it. You may be prompted to sign in to the account when you first run it.
However, some apps need to install support files in certain locations in order for them to work. If that's the case here, the second option isn't likely to work.
You may want to check out FNable as it offers similar functionality.
Note: I have no affiliation with this app whatsoever.