Mac won't autocorrect 'hte'

This has been going on for way too long and I'm hoping someone can help me. For whatever reason, the last two Macs I've had have stopped autocorrecting the word 'hte'. I could of course just learn how to type 'the' but I feel like since the computer is autocorrecting everything else I type, I'm not sure why it is so difficult to correct this obvious typo. This is seemingly the only word my Mac struggles with. I could make a text substitution via keyboard in System Preferences but this would only work for certain apps (and it wouldn't cover all the different permutations that I would need like Hte etc.) I've tried looking and I think the word isn't in my dictionary and I can't 'unlearn' hte so I'm not sure what's wrong. Has anyone a solution to fix this?