You might see this happening if you're running ExtendSim on a Windows OS version prior to 8.1.

To correct this:

Right-click on your desktop

Go to Display Settings

Scroll down to Scale and Layout and Change the size of text, apps, and other items to 100%.

If you have multiple ExtendSim licenses on your computer (for example a Model Developer Edition and an Analysis RunTime version), it is generally better to open the ExtendSim license you want to use first, then open the model. If you double-click on a model file, it will open the last ExtendSim license installed.

If the proper version of Excel is not installed on your computer, you will see the error "OLE CreateObject Not Successful" when you try to access an Excel spreadsheet from within ExtendSim. Possible causes of receiving this error are:

Excel is not installed on your computer.

Excel is installed on your computer, but the installation is damaged. In this case you will need to reinstall Excel.

A “click-to-run” version of Excel is installed on your computer. This version does not support communication between outside applications such as ExtendSim and Excel. You will need to uninstall your click-to-run version of Excel and install a full version of Excel. Instructions for this can be found at

The error "Run-time error 429: ActiveX component can't create object" might occur if you try to launch ExtendSim (as a server) from an outside application (as the client) in an ActiveX/COM client/server process. In order to interface with Excel or other outside applications using ActiveX/COM, ExtendSim must be registered as an OLE/COM server. Many companies restrict an employee's application permissions to the most basic. To register ExtendSim as an OLE/COM server, you must launch ExtendSim one time with Administrator permissions. To do this, right click on the ExtendSim.exe file and select "Run as: Administrator" (you'll probably need a password from your IT department).

Because ExtendSim has its own compiler, it executes compiled code. Windows can interpret this code as data, rather than code, that is executing. The default setting for Data Execution Prevention (DEP) is "Turn on DEP for essential Windows Programs only." Some Windows installations don't use the default; this causes a problem for ExtendSim. In certain cases, ExtendSim will crash upon launch and return the error message "Unknown msg Unknown block". To correct this problem, follow these instructions.

From the Windows Control Panel, find "System & Security or Maintenance".

Click "System", then go into "Advanced System Settings".

Under "Performance", click the "Settings" button.

Select the "Data Execution Prevention" tab.

Select "Turn on DEP for essential Windows Programs and service only" ...OR... Select ""Turn on DEP for all programs and services except those I select". Then, Add "ExtendSim.exe" to the list.