Spell check returns back to do not check

Question

This is an incredibly straightforward problem but couldn't find a proper solution for it.

Here is the deal, I am receiving a software generated content in docx format. My system default language is English. What I do is selecting all stuff by ctrl+a and setting the proofing language to English. When I apply this, some parts of the document are still ignored. When I select them to apply English for proofing, I see a filled square icon on the "do not check spelling" option.

What causes this and how do I overcome?

Note: I tried to copy all stuff and paste it to a blank document and it automatically detects the errors but still facing the same problem on some paragraphs.

Answer 1

What version of Microsoft Word are you using?

On 2013, hover your cursor and click on file which should be on your top-left, then you select options. A window should pop up, click on proofing, you should find your solution there.