start up disk not mounting

Hi there

I hope someone can help. I use an SSD as my start up drive (which now has high Sierra on it).

Today I did a custom boot from the old Mac hard drive as I had some files I couldn't find and wanted to see if they were on the old drive.

When I reboot now though my SSD is not available as a boot drive. It is showing in the disk utility but is unmounted.

Can anyone advise on how I can make it available again as a startup drive?

Thanks

Dan

最后更新：2017-10-03 04:20:54