I didn't find a definitive answer in the searches so here I am.
It might not be fair to say the Siegfried Line worked - Germany still lost - but from what I've read it was much more effective in stopping allied attacks than the Maginot line, despite the fact that the Maginot line was far superior in its hardened defenses. Why didn't the allies just go around, like Germany did with the Maginot Line?
There was still bloody fighting on the Maginot Line in 1940, that cost the Germans pretty dearly. Later on, the Germans made use of some of the fortifications in the battles along the frontier in 1944, and the US 6th Army Group used them to defend against operation north wind in Jan. 1945.
The Siegfried Line was extended in 1944, covering much of the German border in the west, whereas the Maginot Line only covered the Franco-German Border and some other areas.
EDIT: in fact it might be better to distinguish between a Siegfried Line and the West Wall. The Siegfried Line was built before the war, covered the Franco-German Border, and was somewhat dismantled to provide materiel for the Atlantic Wall. The construction of the West Wall began after the Allied break-out from Normandy, building upon and extending the Siegfried Line beyond it's original parameters.