ORIGINAL:
Have made several videos successfully but suddenly my [render] button does nothing but change my lowest panel from the editor to the result view
https://i.sstatic.net/KSN98.png
changes to
https://i.sstatic.net/lUEHN.png
I also noticed it does pop up "Sequence Render" for a very fast moment in place of the blender version above preview. I've never had this happen before and when I try to find previous mentions for help I get bogged down in threads about 3d rendering. I've not changed my settings except to increase the Sequence/Clip Editor Cache. I've checked my properties to make sure those are the same as before. Dimensions, fps, start and end frames, output folder is correct, encoding is the h264 preset, ac3 audio.