Hi @frkca,
Indeed, a renewal count as a "new certificate" for the 20 certs per week rate limit but as renewals are always allowed you should consider issue new certificates first and then renew your certs as they always will be issued.
I think the rate-limits page Rate Limits - Let's Encrypt should be re-worded to show this behaviour on renewal procedure.
You have several topics where more people have the same issue and some tips to avoid to reach this limit
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Cheers,
sahsanu