Had the same thing happen with my wife’s Apple Music 3 month trial.

She accepted the trial, then went into settings to cancel the subscription so she wouldn’t be automatically charged at the end of 3 months.

With no warning, the subscription was then completely cancelled with no ability to use the rest of the trial. (Unlike some other Apple trials.) When asking Apple Support about this, they referenced an obscure sentence in their terms and conditions. They could do nothing to re-offer the trial to my wife. So consumer hostile.