No error occurs but HydraCAD will not properly load and Hcad commands do not work.  

A quick test is to select the drop menu [File|New], select the template file 'HydraCAD Imperial Default.dwt'.  

The Drawing Setup window should appear but it does not, it loads straight into a blank drawing.

This is what you should see (press F2 to review the text window);

Instead you only see;

HCAD_ADS r4 functions Loaded.

AutoCAD menu utilities loaded.
Requires an integer between 0 and 32767.

3dFitting registry keys found

Requires an integer between 0 and 32767. 
 

When attempting to create a new FSC definition, you get this error message.  Clicking OK closes the command

When a folder sent as a ZIP file is extracted, it's likely all of the files will be blocked by Windows.  This prevents the files from functioning properly. 

You can right-click each file, select PROPERTIES then GENERAL then click the UNBLOCK checkbox, however this may be time consuming if many files are blocked.

This method will describe how to unblock many files at once.  

When opening HydraCAD you get the error;

Exception in hcadmainbase.arx ARX Command

Unhandled Exception c0000027 (c0000027h) at address aca746e7h

Drawing Setup dialog doesn't load

No error but when the HydraCAD template is selected, it goes straight to the drawing and command prompt, it doesn't ask for the user to set the scale factor

Selecting any button from the AutoCAD ribbon creates the fatal error.  Typing or using a toolbar does not create the error. 

AutoCAD Error Aborting

FATAL ERROR: Unhandled e0434352h Exception at 6C6CCF19h

Sometimes followed by;

The program is missing Tool Palettes and Ribbons.
The drawing may briefly open and then crash.

Background changes to gray and navigating drawing becomes sluggish after using the Newforma Konekt add in.

I can't find the 'Sentinel Product Key' for my Gemalto entitlement. 

When connecting a hard pipe armover to a flexible sprinkler connection (FSC), the flex hose doesn't continue straight, instead it immediately turns 90° before curving back and down to the sprinkler head.

Even with setting the connection to OVER-DOWN

When selecting a vertical pipe/riser nipple hydrapipe, the PROPERTIES window shows "no selection" instead of "hydrapipe"

You may notice that you cannot use the 'change length' command (CL) or cannot rotate riser nipple (RRT)