His - Denim Blue A220 AMG Line Premium / Hers - Obsidian Black R172 SLK55
I'm assuming that you're trying to open it from the front and hinge it upwards towards the rear bulkhead after releasing the catch under the front edge?
It does actually lock with the central locking (so you can leave the car unattended with the roof down), so it may be worth locking and unlocking the car again to see if that frees it up?
Cls350cdi in palladium,C200k in tenorite,Slk320 in red.
Things are so much easier now the owners manual has arived,after prising the lid open and giving it a good clean and wd40 I then reset the central locking back to factory settings via the keyfob and it's all ok now