ad-activate-on is an alias for `ad-activate' in `advice.el'.

(ad-activate-on FUNCTION &optional COMPILE)

Activate all the advice information of an advised FUNCTION.
If FUNCTION has a proper original definition then an advised
definition will be generated from FUNCTION's advice info and the
definition of FUNCTION will be replaced with it. If a previously
cached advised definition was available, it will be used.
The optional COMPILE argument determines whether the resulting function
or a compilable cached definition will be compiled. If it is negative
no compilation will be performed, if it is positive or otherwise non-nil
the resulting function will be compiled, if it is nil the behavior depends
on the value of `ad-default-compilation-action' (which see).
Activation of an advised function that has an advice info but no actual
pieces of advice is equivalent to a call to `ad-unadvise'. Activation of
an advised function that has actual pieces of advice but none of them are
enabled is equivalent to a call to `ad-deactivate'. The current advised
definition will always be cached for later usage.