MrsS,
The dotted cross hairs on the chart indicate that there is conflicting information in FF analysis of your O day. Looking at your chart it is mostly likely the result of your fertile CM not coinciding with the temp rise. (From memory) There needs to be 3 days of sustained temp rises (which is indicated on your chart). FF usually gives a reason for the dotted cross hairs... can you see any explanations?

This section may assist....
FF FAQs

I wish I could give a more definitive answer - but I HTH