Hi and welcome to Arturia forums.
I don't have a Arturia Controller, but the following works for me.
In B3 i in example can set the Leslie/ Rotor speed and the Brake to be controlled by my X/Y pad. Then when i open Analog Lab, then it work the same without doing anything else, if everything else is in order.
Which OS and DAW do you use?
Which midi CC have you set in B3 for the parameter you wish to control? By default leslie/ rotor speed is set to midi CC 1 (modwheel).
Are you sure it's not a midi CC that's reserved?
Have you mapped the midi CC you use for you AUX for a speciel DAW system?
Are your AUX using the same midi CC - in Analog Lab mode?
Also have you read Analog Labs manual from the bottom of page 41 and the top of page 42?
FYI. You have posted in a forum for a legacy Analog Lab. There is a forum for the current Analog Lab 4 higher up the forum page.