I have tested with a small animator controller. This layer has two states, the first one () has a parameter driver that writes to the parameter and it will transition to the second state () when is modified. Therefore, the transition should occur finally. However, the transition will not occur.

There are duplicated parameters in this controller. It seems that they are preventing parameter drivers from working. When I removed one of them, this controller worked as I expected.

It is a bit hard to add duplicated parameters to an animator controller, but it is not impossible. Could you fix the Parameter Driver to work or validate controllers before uploading?