Disappearing Telephone numbers

Disappearing Telephone numbers

Hi First day with ZOHO, so perhaps being dumb!
 

I have imported contacts from CSV and initally when they appear in the contact list it is with their associated Telephone number. These then dissapear. The same happens when I go to an individual contact the phone number is there for about a second and then goes.
 
I am running skype on my computer, has that got anything to do with it? So the numbers have to be in a specific format?
 
Andy