Connections to HTTPS sites causes 603 error - even with SSL enabled

Hi all
I upgraded my firmware on my SIM900 module so that I can use AT+HTTPSSL=1. The command returns OK and appears to be recognized. However I still have issues when trying to connect to certain secure sites.
For example this example (from https://www.youtube.com/watch?v=cpgQOmQwUL8&t=344s&ab_channel=iforce2d works fine (with my APN parameters):

 AT+SAPBR=3,1,"APN","Justworx"
 AT+SAPBR=1,1
AT+HTTPINIT
 AT+HTTPPARA="CID",1
 AT+HTTPPARA="URL","http://www.iforce2d.net/test.php"
AT+HTTPACTION=0
AT+HTTPREAD=0,34

returns: +HTTPACTION:0,200,35

But this code returns a 603 code:

AT+SAPBR=3,1,"APN","Justworx"
AT+SAPBR=1,1
AT+HTTPINIT
AT+HTTPSSL=1
AT+HTTPPARA="CID",1 
AT+HTTPPARA="URL","https://sherver.co.za/time.php"
AT+HTTPACTION=0

I am connected to the GPRS context and can get an IP address if I use the AT command to check.
My firmware is: Revision:1137B06SIM900M64_ST_ENHANCE
Any ides anyone?
Should I use a different module?
My Sim is a Justworx IoT sim
Regards
Russell