When Cycle shows “Supercritical condition — subcritical cycle invalid” or “Outside the property table — no cycle solved”, no cycle has been solved at the temperatures entered. Save design stays unavailable until one is.
Supercritical condition
The condenser or evaporator temperature is at or above the highest temperature Kelvin reads the refrigerant's saturation line at. Above its critical point a refrigerant has no liquid–vapour phase change, so it can't condense, and no subcritical cycle exists there. The notice gives the refrigerant's critical temperature and the limit, which for a refrigerant on a table is the table's last row, just below the critical temperature.
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Lower the condenser (or evaporator) temperature below the limit the notice gives.
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For R-744 in a warm climate, choose Transcritical CO₂ (R-744) under Cycle type: a gas cooler takes the place of the condenser.
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Or choose a refrigerant whose critical point sits well above your condensing temperature.
Outside the property table
Most refrigerants are solved on a saturation table bundled with Kelvin, and a table is read only between its own rows. A temperature below the table's lowest row would have to be extrapolated, which Kelvin doesn't do: the figures would look like the rest and stand on nothing. The notice names the temperature that's too low, such as the evaporator's or the condenser liquid's (the condensing temperature less the subcooling), and the table's lowest temperature.
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Raise the temperature the notice names to the table's lowest temperature or above.
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Or choose a refrigerant whose table reaches your evaporating temperature.
A state the table can't reach elsewhere in the cycle, such as a flash pressure past the top of the table, is refused the same way, with the reason in the notice.