If your pendulum will not extrude, there is most likely a disconnected line somewhere in your pendulum sketch. One way to possibly check this is to use the Sketch Doctor feature in Inventor. In order to do this, first edit the sketch of the pendulum, and left click and drag to highlight the entire sketch. Then, right click anywhere and select "Sketch Doctor."
Click "Diagnose Sketch", make sure that everything is checked, and then click Okay. Cycle through the list of errors by left clicking on each one, and pay attention to the segments of your sketch that it highlights. The highlighted line segments show where breaks in the sketch occur.
Highlight one of the open loops, click next twice, then select "Close Loop" and click finish. Click "Okay" on the close loop instructions that pop up. Now, select the adjacent line segment to the portion that was highlighted by the sketch doctor in the previous step. In my case, this is the left side of the loop. A "Gap Between Points" dialog should pop up, and just select Okay to allow Inventor to fix the opening in your pendulum. After completing this for all open segments, your figure should now be completely closed and ready to extrude/begin the export process. | 
