1986 560SL Trunk jammed closed
 

1) Button is out and can be pushed in, springs back out but does nothing.
2) Key goes in button but will not turn either direction. Yes it is the correct key.
3) Lubed lock, vibrated, heated, no change.
4) Vacuum system to trunk not working either, vacuum pump can not establish vacuum on line.

Rumor has it that there is a secret location behind the license plate which can be drilled to gain access. But after 4 hours of searching I can find no post explaining where.

Post #18: https://www.benzworld.org/forums/r-c107-sl-slc-class/1701910-trunk-lock-issues.html

Yes. The solution is to remove the License plate. Remove the upper Left hand Rubber Plug This is just the plug that is there to cushion the rattle of a plate,
If you know someone with a 107 you will see how this all works.

This gives you access and with a thin rod try to move the vacuum actuator rod to the left it is tricky but worth your time. Best of luck