A bow will not fire (or load up) when it is used in the offhand slot. I put a bow in the offhand slot, and either something with no right-click effect or nothing at all in my selected hotbar slot. I expected the bow to load up and fire when I right clicked, but all the game tried to do was right click with my selected item in my hotbar. You could recreate this by putting a bow in the offhand slot, and right clicking as to fire it from the offhand slot.
Environment
Mac OSX
Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-82923. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.