Hello @snailt-tony
First, you must ensure that your module SIMCOM 7020G supports SNI in a TLS handshake. HiveMQ Cloud requires the TLS-SNI extension (Server Name Indication) to be available. As far as I know, SIMCOM 7020G doesn’t support SNI but maybe the manufacturer has made this feature available in the latest firmware update.
Please refer to the following FAQ post in order to check more information regarding TLS-SNI extension Frequently Asked Questions
Kind regards,
Diego from HiveMQ Team