Edit for future readers: The renewal rate limiting situation has improved since this post was written. You should ignore the quote below and follow the links for more up-to-date information.
There have been 52 certificates issued in the last week:
https://tools.letsdebug.net/cert-search?m=domain&q=centiva-test.ca&d=168
To make sure you can always renew your certificates when you need to, we have a Renewal Exemption to the Certificates per Registered Domain limit. Even if you’ve hit the limit for the week, you can still issue new certificates that count as renewals. An issuance request counts as a renewal if it contains the exact same set of hostnames as a previously issued certificate. This is the same definition used for the Duplicate Certificate limit described above. Renewals are still subject to the Duplicate Certificate limit. Also note: the order of renewals and new issuances matters. To get the maximum possible number of certificates, you must perform all new issuances before renewals during a given time window.
Your domain is in an awkward situation. You have to juggle the scheduling carefully, or use fewer certificates, or ask Let's Encrypt for a rate limit adjustment.