No image on TV monitor

Apologies for this question.  I should have been able to find the answer but haven't succeeded. 

In playing back from Premiere 6.0.5 I'm not seeing an image on my TV production monitor, which is fed by a Matrox MXO2 Mini Max.  Often (but not always) I also get no sound (in these cases, I don't see modulations on the audio meters in the Premiere interface).  I'm sure the relevant settings exist somewhere but I can't find them.  I do see the Matrox device under "Playback settings," but even though it is selected, there is no image on the TV monitor.  The Matrox device works perfectly with Avid Media Composer 6.5.4 and also with After Effects.  What am I overlooking?

I'd appreciate help since I've struggled with this problem off and on for several years.  Sometimes it's OK, sometimes not.  And the unreliability of the audio is especially frustrating.  I've tried to read whatever I can find on the web.

Many thanks.

ALFRED GUZZETTI

Mac OS 10.8.5

Mac Pro mid-2012

12GB RAM