My friend Murphy continues to be a member of every film crew that I'm on, and loves to throw new problems at me while I'm trying to finish up a feature.
Over the last couple of days, I have not been able to import sequences from other projects. I follow all the standard steps, and the Dynamic Link menu comes up. But once I select the sequence, it acts like it's doing something, but the sequence doesn't show up.
I've done this hundreds of times with no problem, but no dice this time around.
A bug has been introduced in CC2018 - especially the 12.0.1 version - where importing projects and sequences can fail. We reluctantly had to upgrade to CC2018, but not to the 12.0.1 version, as importing projects and sequences was part of our workflow.
If you're on CC 12.0.1, I would suggest downgrading to the ash 12.0.0 version and see if that works for you, or go back to CC2017 where importing is fine. Another thing you could try is to tick the 'Allow duplicate media during import' option in the 'Preferences' 'Media' tab. This can help as sometimes if it is not selected it will not import sequences, though in previous versions I would not want it to do this.
The bugs a pain, and we wouldn't have upgraded to CC2018 while unfixed, but one machine had used it on key projects which forced our hand. There is also a thread about this in the Adobe forums that you might like to read.