What looked like an issue on Rachio’s end, ended up a change on WU side, whereas new stations now have to pass a QC (quality control) process before they are shown as a choice via API. This process takes a week. Pwsweather has since followed suite and implemented a similar QC qualification, creating a similar delay for Gen 2 & 1 users.
A workaround exists (link) if you are not afraid of a command line. Otherwise the best bet is to wait. Note on the workaround, with Gen 3 controller, you need to omit the “PWS_” prefix within the weather station name.