conditional inclusion pcell with cyclic button

I've been trying to reproduce what's in Solution ID: 1802619 (cadence community), but I can't. When I execute the pcell, the callback gives the following error:
CDF: An error occurred when evaluating callback.
Callback: number->callback => changeCheck()

Message: *Error* putprop: first arg must be either symbol, list, defstruct or user type - nil

number is my CDF parameter defined as cyclic with two options.
any ideas?
thanks
Mauricio