Acubench 9.1 used to have an issue with the license file.

As a matter of fact, extend 9.1.0 and 9.1.1 contains AcuBench 9.0.1.

You must expand the AcuBench license code and key with a 9.0.1 activator.
For these releases, there is a 9.0.1 activator included in the AcuBench directory.

The related acubench.alc file must contain:
#  Product........: AcuBench
#  Version........: 9.0.0

and usually is located inside this directory:
%allusersprofile%\\Micro Focus\\extend\\9.0.1\\x86

This issue is now fixed in 9.1.2.1.

So, this release and later need a 9.1.2.1 license which must contain:
#  Product........: AcuBench
#  Version........: 9.1.0

This acubench license file is located in this Windows directory:
%allusersprofile%\\Micro Focus\\extend\\9.1.2\\x86