Has anyone used Clear Blue Digital Advanced OPK?

Amy • 31, hopeful to be a mommy someday!
Tried the Clear Blue Digital Advanced opk this month.  I got the smile for 2 days followed by the flashing smile.  We did the BD all 4 days in a row but no luck :(. Does anyone have advice? Is it best to BD every other day?  Morning or evening?  Has anyone else liked this or other opk's?  Thanks much!