>I may be wrong in this case, but I have seen many automation cases where you must pass a parameter, even if the the parameter value isn't important by itself. Try
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upt.Cancel(.T.)

I tried but got same error.
Image attached.

Maybe it is possible to put code to call it in Container class which hosts it or into come upt.ocx method in hosted control.
Or use hex editor to change Cancel name to somethind other and re-register upt.ofx using regsvr32 upt.ocx

Posted also in

https://stackoverflow.com/questions/56093018/how-to-call-cancel-method-of-activex-control-from-foxpro