Chosen upper working pressure is lower than what it should be according to the input value. Please check these values and amend accordingly.
Selection of a solution is not possible as the upper working pressure and lower working pressure are too close together, or even overlap (lower working pressure based on static height, minimum pressure at highest point and evaporation pressure > upper working pressure).
The expansion pipe design should have a higher value than the system operating load.
The return temperature should not be higher than the maximum operating temperature.