Can you give more details? So the Elgato was working and now does not work after an update to OBS? Update for the Elgato driver/software? You have to give some sort of description if you are looking for help.
So if it was working and is not working now because of an Elgato software update, try reinstalling it. Did you try all the basics? Turning off and on your computer. Restarting OBS. Checking to see if the Elgato captures in the Elgato software. Did you try it in any other programs in general? Have you go into the advanced settings in OBS to check those settings?