When raising to 3D, you get the error message, "Error loading the Error GUI has occurred.  How ironic."

The drawing will raise to 3D, but you won't see the error dialog window.

Trying the Show Model Errors command (SME) produces the same error

Error occurs when using some commands.

Autodesk has just released AutoCAD 2026.1.2 - and it breaks HydraCAD. It includes a major programming change by Autodesk that will require a lot of work and a large update by us. That update is being worked on right now, along with a version of HydraCAD for AutoCAD 2027. Both are now affected by essentially the same programming change.

BinaryFormatter serialization and deserialization are disabled within this application. See  https://aka.ms/binaryformatter for more information.

Other commands with this error;

Sprinkler Layout dialog (SL command)

Trying the DDL command gives the error; 

Usage: (acad_strlsort <list of strings>)

Error bad argument type: consp nil

When importing a Persistent Model into Revizto, none of the riser nipples are visible

During the install of HydraCAD V56/57/58, the user is greeted with the message below.  Following the both sets of instructions of opening and closing AutoCAD, and running a repair of AutoCAD do not make a difference.  You'll still get the error message.

V56 = R23.X
V57 = R24.X
V58 = R25.X

V57 install will say;

Neither AutoCAD 2021, 2022, 2023 nor 2024 found (missing registry key:

HKEY_CURRENT_USER\Software\Autodesk\AutoCAD\R24.X).

Please install it before re-running this install

When opening HydraCAD, you only receive this error message and not a HydraKEY error with the golden X.  If you receive a HydraKEY error, search for the linked HydraCARD in that message box as it takes priority.

Security Error: One of the following conditions is possible

HydraCAD is unable to function under these conditions.

• Lock database needs updating in HydraKEY
• Accounting flag on your account
• Hardware lock not plugged in
• Extra ACAD.RX file found in folder in Support File Search Path
• Sentinel driver is missing
• InstallPath registry item set to wrong drive

After AutoCAD opens, press F2 to view the command prompt, see if the text below appears.  If yes, see solution 1.

Could not find file HCAD_ENV.INI

Is 2024; error: no function definition: PRINTEM

When the OK button is clicked from the AutoLIST Setup window, it'll either hang/freeze or crash with a Fatal Error

Unhandled e0434352h Exception at 25CE17Ah

When raising to 3D, the drawing hangs.  On the progress bar at the bottom, it may be stuck at, "Creating entry for mains database"

If you turn off the Show Fittings in Model option found in the 3D Modeling Settings window (3MO command), it likely will create a model.

The only option is to End Task AutoCAD to stop the process.

When setting up a new head, the dialog that displays the head symbols to be selected appears, is empty, and then drawing crashes,

When attempting to open HydraCALC Sizer, you get this error;

Error:260:0:0

"Well this is new, not sure what's happening with your hardware lock, please get a current 'fix file' from Hydratec"