MacBook Pro 2012 SSD upgrade issue, disk empty after restore

[Kiwi0024]

Hi guys,
I want to upgrade my MacBook Pro 13” Mid 2012 by replacing the original HDD with a Crucial BX500 SSD. Using recovery mode and a USB to SATA cable I initialized my SSD (APFS). Then I installed Mac OS X Mojave and continued like a new device. With Migration Assistant I moved all the things back to SSD and I selected it like the starting disk I want to use. I shut down the Mac and I replace the HDD with SSD but when I try to turn it on the disk is unreadable. In recovery mode the disk is back to MBR(Master Boot Record) and it’s empty. What’s the problem? How can I fix it?

 

[Audit13]

Install the drive inside the machine. Partition with disk utility from Internet recovery, install an os to see if this allows the MacBook to boot from the internal drive.

 

[Fishrrman]

You don't want to use MBR.
For Mojave, I believe that you want APFS, GUID partition format.

Here's what I suggest you do:
a. Put the old drive BACK INTO the MBP for now, so that it's bootable again. Yes, I know "it's work".
b. Once that's done, boot it up and connect the SSD via the adapter cable
c. Now, open Disk Utility and ERASE the SSD to "Mac OS extended, GUID partition map" (this will get changed when you install the Mojave OS to APFS file system)
d. Now, boot to INTERNET RECOVERY (NOT "the recovery partition") by rebooting with the key combination "command-OPTION-R"
e. When you get to the utilities menu, open the OS installer and "point it" at the EXTERNAL SSD
f. Let the installer do its thing. It may involve one or more reboots and several "progress screens". BE PATIENT
g. When the install is done, you should be booted to the SSD with the setup screen waiting for input.
h. Begin the setup. At the appropriate moment, setup assistant will ask if you wish to migrate data from another computer or drive. YES, you WANT TO DO THIS
i. "Point the way" for setup assistant to your INTERNAL (old) drive that has the data on it. It takes a while for setup assistant to "digest" everything. Again, BE PATIENT.
j. Select what you want to bring over and let setup assistant do its thing.
k. When done, you should see a login screen. Login and things should look as they did on the old drive, with your desktop and data "all there in front of you".
l. If things "look as they should", NOW it's time to power down, and "do the drive swap".

Important:
When you first reboot with the SSD inside, you need to hold down the option key until the startup manager appears, then select the new SSD with the pointer and hit return.
When you get logged in, go to the startup disk preference pane and RE-designate the SSD as the "new" boot drive.