A friend had the same problem on their 94 Discovery 39L. As already mentioned, I used a screwdriver to pry out on the awning cover while someone else pressed the extend button. Once the awninig broke loose, I lubed everyrhing with sray liquid silicone. Since then every month we spray lube the joints. All has been fine since.
Jim and Lynda, (Sophie, Jake, attack trained killer Shi-Tzus :-))
2003 Fleetwood Expedition 38N 2005 Saturn Vue