The Minitab installer appears to run ok under Crossover.
Minitab is activated by registering a code on the Minitab activation server.
Under Crossover, it appears that Minitab does not successfully contact the server. Minitab support checked the server log at the time I attempted activation, and there was no record of my contacting the server.
Normally, when Minitab is offline it can be activated by a challenge / response mechanism. However, this does not get invoked under Crossover when the internet is disconnected.
So for some reason, Minitab under Crossover thinks it is connecting to the server, but isn't, so gets some sort of error condition back that blocks activation.
The activation process worked fine when I booted my MacBook with Windows.