Get online support
We'd like to take a deeper look into what's going on and run some tests on your service, @mattsperry.
When you get a sec, could you send me a PM here?
Reset the modem and now everything is working properly.
(Did nothing but hard reset the TPG modem.)
Perhaps something to note for future FTTN -> FTTP connections?
It sounds like you have had some difficulties with your transition to TPG from NBN FttP. It can be frustrating to contact the operator multiple times and receive responses that are not what you expected. It is a bit like playing io games, sometimes patience and smart strategy will lead to better results.