I went directly to the Cleverbridge website and messaged customer support asking them how to stop the subscription since the way they describe in their FAQ (via the link in your invoice emails) does not work and redirects to the Cakewalk closure announcement. Waiting to hear back.
EDIT: It also just occurred to me that since my payment is billed to a checking account that I have solely for online transactions (to avoid fraud) and to which I transfer funds only when making a purchase or when a payment is scheduled, I can just stop the transfer to that account on the day my Cakewalk payment occurs and it will be declined.