I had similar problem. After change disk on Aura Pro x2 not recognized by macbook. Till boot the machine using COMMAND+OPTION+R (helpdesk from OWC). Full instruction below:
-Put the Aura Pro X2 into the machine.[br]
-Put the Apple drive into the enclosure (optional)[br]
-Boot the machine using COMMAND+OPTION+R (this is the specific key combo for High Sierra and above's Recovery mode)[br]
-From there you should see the Aura Pro X2 in Disk Utility. [br]
-Erase/format the drive in APFS[br]
-Exit out to the main Recovery window[br]
-Then, you can install a fresh copy of the OS there in Recovery, and you can use Migration Assistant after it's done, to move your data, OR[br]
-Restore from Time Machine back up