If a 2015 Corolla's touch screen is not working, what can I do as a fix?

There are a number of ways that a touch screen may fail in a 2015 Toyota Corolla, and the reason -- and fix -- is largely dependent upon the method of failure. For example, is Your screen showing anything at all, or is it blank black or blue Is it simply not accepting Your touch inputs A black screen (with no power) is indicative of wiring or overall head unit failure. For this, the fix ranges from a wiring replacement to a total head unit and screen replacement. If the screen shows blue, this points to a software failure -- You'll need to have a dealer re-flash Your automobile with the stock software. If it's not accepting Your touch inputs, it's more than likely caused by a failure of the underlying screen digitizer, whether by temperature, moisture, or impact. Unfortunately, this also necessitates a total replacement of the head unit, as the digitizer for a '15 Corolla is a more expensive replacement than the entire unit.