What I did: Created tags in multiplie notes on my corporate laptop, exported as agenda files, and import on my iOS/iPad. Then search for the tag.
What happened: Imported document will not happen in the tag search results. They do appear in keyword search results.
What I expected: Search by tag works for my imported notes.
Things that might be helpful to know (Agenda version, OS and model, etc):
1.3. Latest MacOS, iOS 11.3, iPhone X.