I HATE that when that happens. To the best of my recollection: I just put in a cup of chicken broth (or water or other liquid), some butter, some salt and pepper (if you want) and your sliced cabbage (I like about 1/4 to 1/2 inch thick “noodles”) into the Instant Pot and seal it. Select “Pressure” and cook from 5 to 10 minutes depending on how tender you want the cabbage to come out. As soon as it is done cooking, immediately “quick” release the pressure.
These are the “noodles” I use the most often.