I have a wifi gateway that connects to my mqtt server with mosquitto. But when I enable the certificate it does not work. I use SSL to self sign them and they work with mqtt explorer.
Are you using the NCD MQTT gateway?
Are you able to monitor, log and share the serial output of the gateway?
When configuring the gateway via wifi, are you using the right port and uploading the right certs as the appropriate root cert / private key / device cert ? (Please describe what you are associating with each when configuring.)
The information @ybakos requested would certainly help troubleshoot your problem.