Why no cover line?

Lauren

I’ve done this for a couple months and I should have a cover line but there isn’t one, any ideas as to why I don’t? TIA!! :)

UPDATE:

Still no cover line, still don’t know why. I have months every now and then where I don’t ovulate but there’s many months that I do and I get the cover line. To get a cover line you need three days of a temp higher than the highest over the past 7 days. So I should have a cover line, even though I know it dropped for a few days it came back up and don’t know why there isn’t a line.