Graduate school Conditional Acceptance
In the universities I've been affiliated, conditions are strictly enforced. If you fail to meet the condition, then the offer is withdrawn. You can appeal the withdrawal, but an appeal will be granted only insofar as procedural irregularities were judged to have taken place. The conditions itself can't be appealed.

I do not know enough about your personal circumstances to comment on the issue of repeating a course. However, it seems to me that repeating a course means that you won't be available to accept the offer and most offers are time-bound.

Good luck to you.