Ok:
I have a certificate that expires in 20 days.
Certificates were generated by DNS-01. So according to your answer in:
since you will typically renew after about 60 days then you won't (currently) need to perform a challenge on your first renewal.
I thought that I was able to renew the certificate with no need of a new challenge, I mean: change txt record in dns configuration.
But I've tried using acme.sh and failed, and now if I've understood well, you say that yes, I must to generate a new challenge, if my certificate has not expired, I don't understand why txt record is expired too.
Am I missing something?
Thanks in advance