When I try to switch “Operation” to “On” it does send a GET request to /sprinklers/index.php?action=en_on, and it gets back a response of “0”, if that narrows it down at all.
I’ve updated to the latest version (1.0.7) (following https://github.com/rszimm/sprinklers_pi/wiki/Upgrading), deleted my cookies, and now I get a big red “System Disabled” banner at the top, there are no stations listed, and if I try to turn on manual mode or turn on “Operation” (a new setting as far as I remember), I get a warning “Error communicating with Sprinkler. Please make sure your Password is correct.”