Associating .acu extension with 32-bit 9.1.0 Runtime is not working on 64-bit Windows.
The installation was made from the 9.1.0 64-bit ACUCOBOL-GT archive as there was a need for 64-bit AcuXDBC. However, the COBOL application requires the 32-bit Runtime.
When double-clicking the .acu program file it gives an error about a missing Runtime license. There are licenses for 64-bit AcuXDBC and 32-bit Runtime.
The Windows file association was made again manually and specifying .acu files open with C:\Program Files (x86)\Micro Focus\Acucbl910\AcuGT\bin\wrun32.exe. However, when double-clicking the .acu program file, Task Manager shows that it is still starting the 64-bit Runtime in C:\Program Files\Micro Focus\Acucbl910\AcuGT\bin\wrun32.exe.
The file association apparently only takes the executable name and then gets the path from the registry entry here:
To resolve start regedit, navigate there, right-click on (Default) and select Modify, then change it to:
"C:\Program Files (x86)\Micro Focus\acucbl910\AcuGT\bin\wrun32.exe" "%1"