Hive Mq Cloud with certificates

Hi Everybody, I am new of this forum.
I am trying to use the HiveMQ Cloud broker with some devices.
Most all of them work ok with credential and TLS and no certificate (as required by the HiveMQ Cloud free account).
I have a couple of them who do not accept the missing of the certificate while selecting the SSL/TLS option.
Is there any way to get at least the HiveMQ CA file to allow the working even with these devices strictly willing (in case SSL/TLS is selected) to have the certificate file?
Thanks for your help,