Simano Nexus 3 speed 1st hear failure

Simano Nexus 3 speed 1st gear failure

My Shimano Nexus 3 speed finally failed after 3 years of hard riding. 1st gear no longer works, but 2nd and 3rd are fine. The hub was under water during a hurricane last year, but I don't know if that was a factor. Anyone know what part is likely to be the culprit? I've never worked on these and have no idea how to diagnose the problem. The bike is fine on the road without low gear, but I use it a lot when riding trails, riding in parades, etc.

I've been riding without a first gear for a week now, 2nd and 3rd are holding up so far. The upside is I now have a neutral which is helpful when you start the engine and it revs past clutch engagement. As soon as I get my other bike up and running I'll pull th wheel and check it out.