Signs that a gas appliance is not receiving enough gas include a weak flame, a flame that goes out frequently, a yellow or orange flame instead of blue (indicating incomplete combustion), and the appliance taking longer than usual to heat up. These issues can be due to problems with the gas line, such as blockages, leaks, or improper installation. If you notice these signs, it’s important to have the appliance and gas line checked by a professional to diagnose and fix the problem.