Nice work on your first project. I did my first one this year as well. Looks like you are somewhere in Australia or perhaps NZ (just going on the style of AC power outlets).
I think your primary problem is the batteries.
According to
the specifications of those batteries, they are NOT designed to operate in series. 12V operation only.
Connecting them in parallel in a 12V system is fine but not in series to create a 24V, 36V or a 48V battery. Their BMSs are not designed for it (most likely a mosfet voltage rating issue).
To put 12V LiFePO4 batteries in series requires batteries with an internal BMS designed for operating in series (most are not). In general you are better to buy a dedicated 24V battery as it will be designed for it.
Unfortunately you are about to find out that LiFePO4 batteries designed for 24V operation are considerably more expensive than two of the Kogan specials you have.
To keep costs down you may want to consider building your own from 8x individual LiFePO4 cells with an 8s BMS. Just like Will does in his videos. Or buy a pre-built 24V battery from China via Alibaba / AliExpress but that comes with purchase risk as is often discussed on here.
Looking at your set up (you are way better at constructing things than me), it looks like you have a battery DC disconnect/isolator switch but no battery overcurrent protection (i.e. a fuse or DC overcurrent breaker). This leaves your system exposed to BMS protection only and that's a risk. I strongly advise adding overcurrent protection for your battery. Something like a suitably rated HRC fuse in a fuse holder although at these lower voltages an ANL fuse is probably as good.