In testing, my dumplings took right around 1 hour on HIGH to fully cook in the crockpot. Depending on the model of slow cooker you are using, your dumplings may require more or less time since the exact cooking temperature does vary between brands (this may be why your dumplings aren't cooking in the slow cooker as expected). For best results, test your dumplings by cutting them in half to check for doneness as the 60-minute mark approaches.