Chosen Solution
I recently upgraded my stock Macbook Pro’s RAM and HDD from 4 GB of RAM to 16 GB and from a 500 GB 5400 rpm HDD to a 1 TB Samsung EVO SSD. When attempting to open the App Store, it does not open and instead an error stating “App Store quit unexpectedly while using the JetEngineMac plug-in.” I have ran the hardware test and no errors arise. Installation of MojaveOS went smoothly without errors. Installation only took ~30 minutes.
Reinstallation of MojaveOS resolved the issue.
At this point its the first thing I would do. Here’s the needed part MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable and here’s the guide MacBook Pro 13" Unibody Mid 2012 Hard Drive Cable Replacement Don’t forget to place the electricians tape on the uppercase where the cable crosses over and don’t fold the cable! Arc it across the corners.
