Hi @Dan249 the latest firmware is 1805.4, if you do not have this can be downloaded to USB and downloaded that way, https://www.samsung.com/uk/support/model/UE43AU8000KXXU/
However if still not available and tried factory reset may be a particular issue with this model. It comes up via search when inputting wwe on my 2017 model (not that I am particularly interested in watching this myself mind you)
I've just live chatted this very query as I can't find in the apps on my new 2021 QE50Q60AAUXXU.
It seems the WWE app is NOT supported at present as my TV uses the Tizen OS. Currently, it only appears on Android and iOS platforms. So looks like only available on 2017-2020 ish models.
Apparently it will be added in future updates of Tizen OS, but they can't say when.
In the meantime, I'll carry on using the Firestick (or chromecast), which is a real pain when there are so few HDMI ports.