Please note that on 30 September 2021 the current DST Root CA X3 server certificate for communication with the AMQP API will expire at URL amqp.ote-cr.cz:5671 (91.209.101.43).

As part of this change, we recommend that you check whether your client trusts the ISRG Root CA X1 (not just DST Root CA X3) and, in the case of OpenSSL, must use at least version 1.1.0 or higher.

All information regarding the change is also listed at this address : DST Root CA X3 Expiration (September 2021) - Let's Encrypt.