I agree with the above posters that the apparently yearly subscription was severely undercommunitated, and thus shouldn't be considered valid. There are laws for that in the UK, where Piriform Ltd. resides. The company is supposed to provide the customer with all needed information about the product at point of purchase, pursuant to the UK Consumer Rights Act 2015 c. 15 s. 11(1). Retroactive expiration of licenses is likely covered by c. 15 s. 11(5) in the same law, which says the customer have to agree to the change in license terms for it to be valid. Even the country of residence in which the customer resides would likely deem this illegal by their legislation. Anyhow, I'm attaching my own invoice from Cleverbridge, further proofing that no word of a subscription was found.
EDIT: Comparing a product key request from 2016 and a newly inquired one seals the suspicion of retroactive expiration of my license.