Any suggestions for why my "Insert Checked Contacts" does not work? I have it set correctly in settings. Tks.

Hi. This is my first time asking a question. My "insert checked contacts" has not worked for 3 months. In general preferences, under Auto Complete, I have checked (as has always been the case) "Use Address AutoComplete (Default)". I've emailed w/Yahoo help repeatedly -- to no avail. Anyone else have this issue? Thanks for any help. Tara