AWS mqtt issue(cannot able to connect)

I am trying to use MQTT in AWS platform while creating the thing we need to download the root file. In some videos the CA certificate file is different it shows in txt, but the new AWS platform has in .html format. Pasted all the required certificates and subscribed topic but i cannot able to connect the MQTT broker.
Help me.
Thanks.

not able to download the root CA file
help me please
thanks

Sorry to hear about your problem but it doesn't really sound like a Node-RED issue