The travel agent probably just has "not available" shown in their system, without any finer details of why not. So if the commercial basis is it's been decided to market the flights only for round trips from the UK, tied up with accommodation, that doesn't necessarily come through.
More generally, regarding travel agencies, I long ago gave up placing any credence on their descriptions of the operational side of what it is they are selling. Our corporate one a while ago told me I "had to" check in at London City minimum 3 hours before an 0700 flight to Dublin "Because it's international". When pointed out the terminal doors are not even unlocked until 0515 in the morning they just mumbled.
Last edited by WHBM; 3rd Dec 2018 at 14:05.