OE uses the spell checker from Word or similar programs for its own use.
Perhaps your version of Word is too old?
You can download spellcheckers for use with OE and one or two have been featured on recent PCA magazine cover disks.
HTC U12 Plus review: Hands-on
Brilliant (and Weird) World Cup 2018 Art and Design Projects
iPhone 8 vs OnePlus 6
TV & Streaming : comment regarder Roland Garros ?