When trying to open the Overrides dialog box, you get this error;

Error: bad argument type: stringp nil

When raising to 3D (S3D command), you get a yellow circle with the message "Takeout of fitting does not match takeout expected for a "??????".  Change fitting of fabrication method"

When trying to insert a specific fitting, you get the error

Could not add this part to the fitting because of missing endprep

then;

AutoCAD Error Aborting

INTERNAL ERROR: !dbentapi.cpp@719: eNullObjectld

When starting AutoCALC, it stops in the v50 Fuel Gauge at step 1a.4 - Calculating Total Lengths. 

Working on the pipe from node #### to node #### with a fitting string of ...

May be followed by a Runtime Error 13 or Runtime Error 5

Your first step of troubleshooting should be to track down the coordinates of the handles (the 4 to 6 character hex code noted after the word node, or pipe, or fitting.  Search for the command FINDME to get these coordinates.

When starting AutoCALC the v50 Fuel Gauge stops at step 1a.4 plus you get a Run-time error 6; Overflow 

Working on pipe from Node ### to Node ### with a fitting of "?" and a diameter of / pipe type of 0.5 / SCHED-40 where the pipe id = ### 

The "####" values represent handles.  It is recommended you use the FINDME tool to find the coordinates of the handles, this will help narrow down the cause of the error.

May also see a Runtime Error 5, "invalid procedure"

When Opening HydraCAD or trying to list a drawing, you recieve any Error containing the following CLSID:

44D62FAE-67A7-4131-BF38-489CDFE44738

Or any of the following HRESULT error numbers:

0x800736B1

0x80040154

0x80070002

0x80080005

0x80029C4A TYPE_E_CANTLOADLIBRARY

When attempting to create a 3D model, you get the error; Please switch to System Model to Annotate Drops and Sprigs plus

System.NullReferenceException: Object reference not set to an instance of an object

at HCADexports.RevitConversion.create_hydrapipes_from_db()

at HCADexports.RevitConversion.create_hydrafittings_from_db(List'1 pipes, List'1 heads)

Unknown fitting in drawing, cannot continue

Type SME at the command line to open 'Show Model Errors' dialog box

When running the "FSC Setup" to "Create FSC Definition". 
Upon finishing the block definition, the block definition is missing a crucial property for "Hydraulic equivalent length is referenced by:". This field will show blank or the default generic text and did not include the HydraCALC pipe/fitting reference information.

There is a missing HydraCALC "ImportExport" directory.

Default line text:
`Hydraulic equivalent length is referenced by: shortname with length number - longname Listing: FM`

Unable to select a pipe or fitting when trying to use the Delete Pipe tool.

When starting the AutoCALC process, you get this error;

Could not find fitting match for Pump Only/Test Point Please check!!

You also see an Accessing Database window with a partial green progress bar.

No Operating Heads of Flows Found!!  Please check...

3D Details (3D Fittings) missing, only the skipoles are showing

HydraCALC is calculating the equivalent lengths wrong 

Step 1a.3 - Fitting Exchange No replacement fitting name for 22E for Sched-10 Note: This could be any fitting or pipe type described in the error. If you click ok at each error, the process will run through without these fittings

After buiding your 3D risers, raising to 3D, exporting to a Persistent Model and Navisworks successfully, your 3D riser is missing, with the exception of the skipoles

Your layers are on and the 3D_DETAIL layer is present, unlocked, thawed and visible, you just can't see the pipe and fittings.  The one customer reporting this said they disappear if the drawing is closed then re-opened.  They'll be visible in viewports as well, just not in 2D view.

See this related HydraCARD also;  https://hydracards.hydratecinc.com/cards/card-1144

Command failure for external command ... System.IO.FileNotFoundException ... File name 'AWSSDK'

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. 
 

Auto Adjust Fittings defaults to unchecked.

layer override set up for this viewport or layer is frozen in "viewport freeze" Layers not displaying

Error 52 trying to insert fittings for calculations. Error 71 disk not ready error trying to use the sizing button. error 52 or 71