Hi Marina,
There are a couple of points.
#1:
Review the languages shown above the double line in the Mark selected text as list. Office can detect only those languages listed above the double line. If the languages that you use are not shown above the double line, you must enable the editing language (turn on the language-specific options) so that Office can automatically detect them.
#2
Notes:
Automatic language detection requires a sentence of text to accurately identify the correct language. Depending on the length of your sentences, you might need to type several sentences before Office has enough contextual information to detect the language and apply the correct dictionary.
Words that are spelled the same way in several languages, such as "centre" in English (United Kingdom) and French (France), might cause incorrect language identification. To solve this problem, type more words in the language that you want, or clear the Detect language automatically check box.
I’m eager to hear back and work together to find a solution.