After you select "Convert Photos to DNG" option, what's the number showed on top of the pop-up window?
It should display the number of photos you are going to convert.
Are you in grid view in Library?
you have to be in the Grid View and do the selecting in there. Selecting in the Film Strip area doesn't really select all the images.
Ah, thank you, I'm using a 2 monitor set up with the second monitor showing the grid view and main monitor showing single image. I can select multiple images on second monitor but.. Changing to grid view on main monitor allows me to select multiple images and then convert all. Thank you so much!