Has anyone missed their ovulation before?

I have done ovulation tests every day since my period ended on the 19th of August. Ive been using clear blue - and all have come up with negative. There is always a dark line and one very faint line, sometimes it's as if it's non existent.

My calendar said that I should have ovulated about a week and a bit ago.

And yet nothing... so when I enter my details into the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a>, it's constantly changing when I should be ovulating (if that makes sense)