Freeze Synth not always available

[John Balich]

In converting Midi to Audio I normally use the "freeze Synth"  option.  This select button is sometimes lit  and ready to use and sometimes greyed out............

I havent been able to figure out the key to having that option available.  I know i can export the midi as audio, but i find the "freeze synth" more convenient.l Thoughts? 

[OutrageProductions]

Make sure that the track driving the VSTi that you want to freeze is the one that is selected and in focus in both Track View and Piano Roll View (if open) first.

(That has tripped me up more than I care to remember!)