2009 Audi B8 A4 Quattro

Engine turns over but doesn't start
- recently replaced spark plugs
- EPC and Check engine lights

Tried using various OBD2 softwares to check fault codes, but it refuses to connect.
I've confirmed that all of the fuses on either side of the dash are intact.

Purchased a new battery, just bought the cheapest one that would fit, didn't think the specifications really mattered.

I live in Australia so things like cca don't really matter. Was going to buy the proper battery but I'm not willing to drop $400 if that's not the problem.

Any help is greatly appreciated as I've tried searching on so many forums for so long.

Thanks