The retractable top will not open - electronic message says to 'visit workshop' on 2003 Mercedes-Benz SL500

Dealership wants $140 just to diagnose the problem. Hoping there is a simple fix possibly related to a trunk closure limit switch that is not engaging. Does not appear related to the trunk 'cover' engagement switch. Would appreciate any thoughts on how to resolve.

Asked by for the 2003 Mercedes-Benz SL500