Double-clicking your HydraCALC icon makes nothing happen.  You do not see HydraCALC open onscreen nor on your taskbar.  

If you open your task manager and see the app "Hyd_prog.exe" open but not on your taskbar, then the application is stuck in purgatory.

If you see entries here, use END TASK to get rid of them.

Another option may be that it's on the taskbar but not on your screen.  That means it's open but offscreen. 

See this HydraCARD to fix that issue;  HydraCARD 565 only AFTER you've checked on the solution below.

When running a calculation, the value for "pressure required" shows a negative value.

After calculating the system, the results show, "Your System Has a Deficit"

System is -nan(ind) psi over the Water Supply Curve

HydraCALC is calculating the equivalent lengths wrong 

HydraVIEW default printer 'yourprinternamehere' was not found, resetting to Windows default.

Then possibly a runtime error 62, Input past end of file

**Trying to calculate a job which was generated from HydraCAD**, you get this error on the first attempt to calculate;

'disconnected pipe'

When trying to run a source calc calculation (find the maximum possible denisity) with a pump as one of the water supplies, you get the error message; 

A source calc cannot be performed if a pump is present.  Please remove the pump or uncheck 'Source Calc' to continue.

Trying to run a calculation gets a Runtime error 13, Type mismatch

You get a runtime error 13 after clicking OK on the results window.

During the install of HydraKEY, this error message pops up.  Of note, if not paying close attention, it looks like it installed properly due to the 'Completed' message at the top and the FINISHED button at the end, but if you read closely, you'll see this information.

InstallShield Wizard Completed

The wizard was interrupted before HydraKey could be completely installed.  

Your system has not been modified.  To complete installation at another time, please run setup again.

Click Finish to exit the wizard