I had an existing segment listed by job title and tried adding to that by 'job title contains' and then put some more terms in there (with commas in between each term). However after submitting this no further contacts were added to the list even though I can see in the full list there are people with those words in their job title. 

Then I tried to create the segment from scratch however the system is now not picking up any contacts for the list despite them appearing in the previous segment.