By ripening, I assume you mean turning blue.

Let them hang for 2-3 weeks after first turning blue and then try them. That's when they get sweet.

The blueberry should be blue all the way through. Check the stem side.....should be no pink there.

On dragonfruit list somebody mentioned something about soil sulfur application increasing brix (fruit sugar). My raspberries weren't sweet enough for weeks and I suspected soil was insufficiently acid so I tossed some sulfur on, and sure enough weeks later I started getting delicious full-flavored sweet raspberries. This discovery has only occured over last few weeks. It seems to me blueberries also prefer soil more acid than 6.6, however it may be rather cool where you are for results to appear on your current crop. I'm sorry I don't know anything more about this sketchy suggestion.