According to our records, the software client you’re using to get Let’s Encrypt TLS/SSL certificates issued or renewed at least one HTTPS certificate in the past two weeks using the ACMEv1 protocol. Here are the details of one recent ACMEv1 request from each of your account(s):
WINDOWS IIS Server
Client IP address: 188.8.131.52
User agent: ACMEdotNET/0.9.1.0 (ACME 1.0)
Request time: 2020-01-21 15:00:16 UTC
Beginning June 1, 2020, we will stop allowing new domains to validate using the ACMEv1 protocol. You should upgrade to an ACMEv2 compatible client before then, or certificate issuance will fail.