Yes, Windows 7 is supported:
https://wyday.com/limelm/help/using-turboactivate/#requirements
https://wyday.com/limelm/help/using-turbofloat/#requirements
>> "Any obvious things to test for?"
Much more information is needed. Is the problem with TurboFloat library or the TurboFloat Server? What is the function that is failing? Exactly what are the parameters being passed to the function? Exactly what is the error code being returned?