When you open a document, you expect to see red squiggly lines below words that the spell check does not find in its dictionary, or words that are genuinely misspelled. You also expect to see green squiggly lines below words that don’t agree with the grammar check.
However, now and then, for some reason the lines don’t appear at all in the document. They don’t even appear below words that should have the red or squiggly lines beneath them. And when you run a spell check, it just says “The spelling and grammar check is complete” when it should have started indicating words with the red/green squiggly lines.
I myself have found that sometimes the grammar and spell check acts up in this way. Fortunately there is a very simple way to fix this problem that I have found on the Internet. Select the text and then briefly change the language. My own preference is to change the type of English from, say, UK English to US English. Then I change the language back again. Bingo! The red and green squiggly lines instantly appear.