This just happened to me too. It randomly stopped working part way through the day. None of my characters can use the bench. I played through to the next day and it still didn't work. I restarted the game and it still does not work. I can use any of my other work stations just fine. Just the workshop bench's menu will not show up.
Really hope this can be patched or fixed somehow. I'm on day 35 with everything upgraded and this glitch make playing any further impossible.