Paid subscription not appearing so I can cancel

It sounds like your subscription was made directly on their website, so it would not be managed by Apple or appear in your Settings to be cancelled by Apple. When viewing their website, this is what it says about cancelling the subscription.

•  To terminate your subscription, you must explicitly cancel it by navigating to the “My Account” section within the App. Failure to cancel your subscription through this method will result in the continuation of billing and access to subscription services until cancellation is successfully completed.
• Cancellation of Service Subscription. You can cancel your subscription for our Services at any time by contacting Customer Support at support@hypnozio.com. Your cancellation request will be processed within 72 hours after we receive your request. You can cancel your subscription for our Services at any time in the App by going to the “My Account” section. Your cancellation will be effective immediately. 

https://hypnozio.com/terms