I own a mid-2015 mb pro, so that should work, right? Why would I get an error message that says “Required firmware update could not be installed. Compatible internal storage is required in order to update.” I have 16 GB of RAM, and have added a 1TB SSD drive that is APFS (encrypted); would these not be compatible? Help would be appreciated, of course, but, maybe more to the point here, is Apple disallowing memory or storage upgrades from outside vendors?