When you updated the application, it might have rendered all the plug-ins incompatible. You need to check in the Systems > Addons > Disabled Add-ons. The Navi will be there in case it's not compatible with the latest version installed. Click it and then trigger the Manual check for updates. If there is an update it should be applied. Click again the Navi entry and enable the add-on. You will find it in the same location in Video add-ons.
I have encountered the same issue with a Raspberry PI v1 B and OpenELEC and I fixed it this way.