Hi,
Please set the Dialogue Manager GameObject's Other Settings > Debug Level to Info. Then reproduce the issue. Do you see the conversation playing? You should see lines like:
Dialogue System: Starting conversation...
Dialogue System: Add link...
Dialogue System: Actor says '...'
Dialogue System: Sequencer: ...
(See the
Logging & Debugging Tips video for details on Debug Level > Info.)
Most likely your dialogue entries' Sequences are configured to finish immediately, either in each entry's Sequence field or -- if the Sequence field is blank -- the Dialogue Manager GameObject's Display Settings > Camera & Cutscene Settings > Default Sequence field. If so, please see:
How To: Control the Duration of Subtitle Text