Known words with accents becoming unknown?

I am reading a book on LingQ in Spanish at the moment and when I imported my chapter for today I noticed the number of unknown words was a lot higher than usual for a chapter (more than double). Sure enough, when I started reading, I saw quite a few basic words like después, había, también etc highlighted in blue that are definitely known words (I am at almost 20,000 known words in Spanish). All of the words in questions have accents in them so this must have something to do with it.

Anyone have any ideas as to why this might be happening? My known word count has remained the same, but I’d rather not have all these words counted twice in my word count.