Drop Down Tab for Fax number is not giving options anymore-the arrow is there but no options appear

Go to Config > Tables > Phone Types.  Double check that the phone types you think should be listed in the drop-down are selected to appear in that tab. Once you double-click/select a Phone Type, check the "Phone Number Type" field.  If you need a type to appear in more than one tab, you will have to create more than one phone type.