If I go to “Video Service” the BM Decklink 2 is there (see attachment).
You can select it AND an Output format.
Apply and back to project - no video.
Open “Video Service” again - Black Magic is un-checked.
Obviously, this problem is not solved as relates to the version 1.6.2.361 Video Engine that comes with 8.5.1.
But it seems I have been able to solve the problem by instead using Video Engine (4 files, videoengine, videodecode, videooutput, and videopreload) versions 1.6.1.344 - form CB 8.0 in place of these files in 8.5.1.