This is a problem on the shuffle, so I don't think it is related to updating iTunes.
Is it possible that you put the shuffle "on hold" (prevents accidentally pressing buttons)? You do this by pressing and holding the Play/Pause button until the status light blinks three times. Repeat this action to unlock.
If that does not help, do a Reset of the shuffle
This is just turning OFF the shuffle, but you need to wait long enough before turning it back ON.
And you did a Reset following the directions I linked above?
If so and it did not help, you can try doing a Restore on the shuffle in iTunes. Select the shuffle in iTunes. The Restore command is on the shuffle's Summary or Settings tab (depending on model). This will erase the shuffle, re-install its software, and set it to default settings. If a software glitch is causing the problem, a Restore should fix it.
If a Restore does not help, the button assembly may be faulty. If the shuffle is a 4th gen that is less than one year from purchase, it is under warranty. If you bought AppleCare with it, the coverage extends to a total of two years.