MBP does not recognize external boot drive

[MK25toLife]

Hello,

I just came back from a 3 week vacation and saw my MBP had all these updates and w/o thinking, I just went ahead and updated. So now my MBP is running 10.13.5, note that this is my work computer.

I do not have my own personal computer as I am just using an external SSD boot drive that is a mirror image of my old computer. As a side note, I am just waiting for the new MBP to come out.

When I plug in the SSD and press hold while restarting my MBP, the SSD does not show up as an option. Before I updated the OS on my MBP, I was able to select my SSD and run it with no issues. My SSD is a step below 10.13.5, so I wouldn't think there would be an issue. This is not a case of El Capitan (SSD) and High Sierra (MBP) - an issue I initially had.

Is there anything I can do to pinpoint what the issue is? This is extremely frustrating. Do I simply have to upgrade my SSD to 10.13.5?

 

[MK25toLife]

Hello,

I just came back from a 3 week vacation and saw my MBP had all these updates and w/o thinking, I just went ahead and updated. So now my MBP is running 10.13.5, note that this is my work computer.

I do not have my own personal computer as I am just using an external SSD boot drive that is a mirror image of my old computer. As a side note, I am just waiting for the new MBP to come out.

When I plug in the SSD and press hold while restarting my MBP, the SSD does not show up as an option. Before I updated the OS on my MBP, I was able to select my SSD and run it with no issues. My SSD is a step below 10.13.5, so I wouldn't think there would be an issue. This is not a case of El Capitan (SSD) and High Sierra (MBP) - an issue I initially had.

Is there anything I can do to pinpoint what the issue is? This is extremely frustrating. Do I simply have to upgrade my SSD to 10.13.5?

I am confused why my bootable disk doesn't even show up when holding "option" during the start up OR in Startup Disk. Any feedback would be much appreciated.

 

[treekram]

Does your external SSD show in Finder under the Devices list after booting from the internal SSD? If so, when you look at the contents of the drive, does it look OK? If it does, open the Terminal app. On the menu at the top, select "Shell" -> "New Command..." In the box that appears, enter:
bless --info /Volumes/[whatever your disk name is that appears in the Finder], without the brackets
and press the "Run" button.

If you have a space in your disk name, put a double quote before /Volumes/... and after the end of your disk name. The results will return in a new window. Do you have a line that says "Blessed System [whatever] is [whatever]? If not, enter, go through the Shell -> New Command and enter:
sudo bless --folder /Volumes/[disk name]/System/Library/CoreServices

If the disk wasn't blessed before, it should indicate that it now is. See if it shows up as a candidate boot disk or not. Disks shouldn't lose their bless setting but if that's the case, who knows what happened?