With the recent update to Teams the spellchecker is not working correctly. It will show the misspelled word but when you click on it there is no longer a suggested spelling popping up. We (Several in the company) have noticed this on the latest update to the following version, Microsoft Teams Version 1.6.00.21970 (64-bit).
I have already gone in and deleted the setting.json file, that will work for a short time 10-20 minutes then back to not given a suggestion.
I am seeing an old issue TM390278 https://answers.microsoft.com/en-us/msteams/forum/all/microsoft-teams-spell-check/337ee648-af60-4cf4-8336-a1c68f3a1d78
I tested if we use the pop out feature and chat in a seperate window spellchecker will work as intended it appear to be the same issue as posted before.