Anytime you upgrade to a new year of Creative Cloud (e.g. CC 2018 to CC 2019), you will need an updated Triple Triangle deployment. If you upgraded without realizing this, you may find that your plug-ins are missing, or that when you attempt to install your previous deployment you get error messages like this:
You can address this issue by requesting an upgrade from email@example.com. We generally respond within 24 hours, and often less.
If you modified your slug styles locally, please attach your latest .ttsx file in a zip when you request the upgrade (if you don't know what this is, you can assume you have not).
Alternately, if you did not intend to upgrade, you can also roll back to the previous version of Creative Cloud by opening the Creative Cloud menu icon, then clicking the drop menu next to InDesign, and selecting Manage > Other Versions.