open the system preferences and go to the Startup Disk panel. Then click the lock so you can unlock the setting and then select your internal SSD drive. Once its set hit the restart button and once the system has bonged disconnect your external drive it should boot up correctly now.
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Open the system preferences and go to the 'Startup Disk' panel. Then click the lock so you can unlock the setting and then select your internal SSD drive. Once its set hit the restart button and once the system has bonged disconnect your external drive it should boot up correctly now.
The alternate way is to hold the option key doing boot that will allow you to access which drive to boot from. Unlike the Prep setting it won't hold.
Ref: [https://support.apple.com/en-us/HT201255|Startup key combinations for Mac]
open the system preferences and go to the Startup Disk panel. Then click the lock so you can unlock the setting and then select your internal SSD drive. Once its set hit the restart button and once the system has bonged disconnect your external drive it should boot up correctly now.
The alternate way is to hold the option key doing boot that will allow you to access which drive to boot from. Unlike the Prep setting it won't hold.
Ref: [https://support.apple.com/en-us/HT201255|Startup key combinations for Mac]