This is an undocumented "gotcha" that has tripped up users with several of the starter solutions. Your template requires each contact record to have a unique serial number (probably in a field called ContactID). When you import contacts from Excel, this field is left blank unless you also enable auto-enter operations during the import. (There's a check box for this in a dialog that pops up just before the import starts.)
If you duplicate a record, the duplicated record get's a serial number in this field auto-matically--which is why the duplicated record works.
Simplest fix is to start over with an empty copy of your current file and re-import the contacts from your excel file, but now with this option enable.
If you have lot of contact records that you've created since the import, you might also find this field, place it on a contacts layout, Perform a find to find all records where the field is empty (Put a lone = operator in the field while in find mode), and then use Replace Field Contents with the serial numbers option to give them all a serial number.