Help with Mail Merge LibreOffice

Hi everybody!

I have a problem with mail merge on Libre office 5.3 installed on Ubuntu 16.04.

Once I inserted every field, I can’t perform Merge Mail on a selected record of the database . I tried on other PC and the option appears. I need to perform Merge Mail only on field thai I need in that moment.
I disinstalled and reinstalled all the Libre Office packages but the same problems persists.

Thanks for help