I’m guessing other WiFi enabled devices in your home are connecting just fine. Sometimes when I run into a problem with one device I do a hard reboot to the modem, router, and any switches in between. This insures and fresh start. Follow the directions to add the timer to your network and wait for any firmware updates.

What is your rain threshold set at? Perhaps it needs adjustment.

Your timer checks for a change in schedule every hour at the most responsive setting. The call for water doesn’t happen until the next time it wakes from sleep and checks if I’m not mistaken.