I have checked your NBN-FTTC 100/40 service on our systems.
There is an open TPG fault ticket already lodged, ref #10472586.
There is also an open fault incident lodged with NBN. It says they have a restoration date for up to 22/05.
Unfortunately if the issue is within the NBN network and the fault is logged, we will just have to wait until that date for NBN to finish their works and fix the network issue.