Using New Outlook on Windows for professional communication and productivity
I have had the same issue, but I have the Office 365 Outlook app actually loaded on my computer.
It happened when I switched to the new view of Outlook. I am ready to switch back to the old view due to this feature not working. I use it all the time.
It shows the spelling error, but does not provide spelling suggestions in the right click pop up menu.
I checked the editor settings and these are all turned on. I also restarted the application.
In the new Outlook for Windows, simply clicking in a word which is flagged as misspelled will display spelling suggestions.
I found that if the message is embedded in the main Outlook window, then this issue occurs (can't bring up right click menus including spell check). HOWEVER, if you "pop out" the message into it's own floating window, then the right click seems to work.