Is it appropriate for a journal to cancel an accepted review request before the deadline?
Is it ethical for journal to cancel accepted review request before deadline?


In some circumstances, it would be ethically required to cancel the review request.  The editor has avoided wasting more of your time by cancelling the request.

"Unforseen circumstances" probably means the authors withdrew the manuscript.

Canceling a review request can also occur when another reviewer has submitted a review which ensures the manuscript cannot be published.