Please can someone explain to me why I get the message 'Sorry, this is a seasonal route March - October, when I try to look at flights for July/August 2015?
Flights ex GLA only operate on certain days, so maybe you are searching on days when they don't operate, although usually if you have the +/- 3 days option selected it will show you the next available options.
If it still isn't working then it is likely to just be a bug, so maybe give them a call until it is fixed.