We cannot become sharks, so we cannot swallow a one metre long fish. And we cannot become God with the wisdom and reach to manoeuvre the willful reprobate into a set of circumstances where the true state of his heart is plain to him and he falls upon the Rock for mercy.
But just because we in the Hebrews authors classroom cannot bring a wilful reprobate among us to repentance does not mean that no one can. And therefore, "It is impossible (for us) to bring that one to repentance", does not mean "It is impossible for that one to be brought to repentance (by God).