My first posting and I need help!

Since I have had my cabrio, (2003 Reg) I have had intermittant problems with the roof. It gets stuck half way and bleeps.
Up until now the very nice man at the Renault garage has fixed it in seconds for me,( there is obviously a knack!)
This time he will not look at it unless I pay £85! Shock horror!

My local garage has had a go - but can't see how to do it.
Any suggestions welcome please.
J the Softop