When i set my Rachio3 up i neglected to turn the rain sensor on (it was connected, just not active). When i activated it it said it was wet even though we hadn't had in train in almost 2 months. I ended up deactivating it soy my yard wouldn't burn up.. in July in Texas it prevented the system from running for two weeks. Yep, it's a bug.
i havent tried as the rachio is usually pretty good at predicting rain if not overly cautious.. and as i said my rain sensor works.. I did have one previously that did not. recommend you check your wiring with a multimeter if it is not working..
But as i noticed it is cork.. and it takes a day or day to dry out. you could easily make your own ... stick a couple of wires in a cork and mount outside.. lol
You should be able to write your own rules in rule machine where you check custom attributes in either ecowitt or one of the openweather etc apps. for rain and then put the rachiio in a rain delay using the buit in function set_Rain_delay to say 2 hours.. etc.. you would use the custom action in rule machine the type would be actuator the device would be the main rachio device..