Why is my Android Keyboard (AOSP) Autocorrect not working?

[AC Question]

I have a Huawei Maimang 5 with Android 6.0. It is using English (UK), I have turned on auto-correction but when I type an incorrect word it doesn't correct it or underline it either. The dictionary is English (UK). On my previous Huawei phone which was a P7 lite the auto-correct was working fine, but on here it seems it isn't even a thing even if I have turned it on.