Check that you have 1024 samples in the buffer.
If you use the plug-in as an insert, the number of tracks in the insert is limited on the different Editors/Hosts.
On Protools, and Media Composer, you can only play 2 tracks in insert with a video.
Beyond that, the warning message AAE-9371 will be displayed, just deactivate an insert track to return to a maximum of two tracks if you use a video simultaneously.
For your information, without video playback, you can edit to a maximum of 4 insert tracks on Protools and Media Composer.