When you switch the weather algorithm to Auto Rain Delay, it will stop calculating watering percentage automatically. As a result, if the watering percentage was 0% before you switched, it will remain 0%. You can manually set it back to 100% (if it doesn’t allow you to do so, switch to Manual, set to 100%, then switch to auto rain delay again). Auto rain delay only produces rain delays and will not affect watering percentage (so it will remain whatever it was before you switched to it).