I recently tried to install Mojave on my Macbook Pro mid-2014. My first task was to try finding Mojave in the App Store, which turned out to be a problem. Searching for Mojave inside the App Store doesn’t return any result. Bizarre!
If you’re in the same boat, you might have to do what I did and find a direct link to Mojave from Apple’s website. I used this one:
The link above will launch the macOS Mojave download page inside your App Store app.
I got the URL from the official Mojave OS page. If the link above doesn’t work go check if they updated the URL since I wrote this article.
It will probably take some time to download the Mojave installer, depending on your connection quality. It took me around two hours.
Note: if you’ve tried to install Mojave before, then you probably have an old (and invalid) installer on your hard drive. If you try to download a new one, you’ll get a misleading error prompt. To get around this, delete your old macOS Mojave file, and then click on the Download button in the App Store to get a new one.
After downloading a fresh copy of macOS Mojave, if you get the same, or a similar error message as before when you try opening the Mojave installer, don’t panic, try restarting your computer.
After restarting, hit up your Spotlight search (CMD + SPACE) and search for “Mojave” to quickly find the install file. Now double-click on it to open the Mojave installer window. It should look like this:
At least that (restarting) did the trick for me.
If you still can’t make it work, there’s a bunch help in this 9to5mac thread.