The error often stems from corrupted C++ libraries that the DLL depends on. Uninstall current C++ Redistributables and download the latest versions from the Microsoft support site.
Troubleshooting should follow a tiered approach, from simple fixes to more invasive system repairs: Problem loading acadres.dll file - Autodesk Forums
Compatibility issues are a common cause.
Right-click your AutoCAD 2021 desktop shortcut and select Properties . Step 2: Navigate to the Shortcut tab.