Welcome to TPG Community!
I've managed to pull up your account using your Community details and and it appears that the SIM is already set to active or has been activated on our end. Have you perhaps tried restarting your phone?
If it still hasn't work after the reboot, kindly let me know of your best contact time & number via private message so I can organise a call back to be made from our Mobile Technical Team.
We'll wait for your response.