Same problem. HTTP client works fine, but not the webapp.
I do see that trying to switch on manual mode in the app flashes a error message for a second: “Error communicating with open sprinkler. Please check your password is correct”.
Known bug, the answer is here: https://github.com/salbahra/OpenSprinkler-Controller/issues/30
Edit the config.php file and change the password there:
#Set OpenSprinkler password
$os_pw = “opendoor”;
Alternative: Change your password back to “opendoor”