Have you copied the text from somewhere else? There may be code or formatting errors in the text, which is not visible otherwise.
You will notice that there is a Ctrl+Alt+X shortcut that will do an automatic spell and grammar check. Click on Tools in the menu and under Spelling and grammar, enable Show spelling suggestions and Show grammar suggestions. A recent update pushed by Google might have disabled it. The feature may be currently disabled in Google Docs. Hit the F5 button on your keyboard to refresh the page. This is a simple trick that may fix web apps related to bugs. Here are some solutions to fix spell check not working in Google Docs problem. The Google Docs menu overrides the right-click browser menu options.
Note that some browsers like Firefox and Chrome also have a spell checker built-in, but they don’t work inside the Google Docs.
For some odd reason, spell check is not working in Google Docs for several users. Fortunately, Google Docs comes with a built-in spell checker. When thoughts are crossing your mind faster than your typing speed, you tend to make spelling mistakes. I frequently use it to write helpful guides for GT. Google Docs is one of the most popular and functional online word processor apps right now.
