My apologies - enableTls returns an int but connect returns a bool. So you seeing a 0 means that it is in fact unable to connect at the connection call. If enableTls is returning 0 before this (aka succeeding), it means that you likely have a permissions problem.
You can get the error code for the connection attempt by enabling debug output in MQTT-TLS.h:
make sure debug_tls is defined as below (just copy paste this below the section where it currently is defined.
#define debug_tls( fmt, ... ) \ Serial.printf(fmt, ##__VA_ARGS__)
This will give debug output from the ssl handshake result and a few other things. I don’t want to take over this thread so feel free to PM me the result and we can follow up on this thread once we’ve figured it all out.