Hi Steven,
To have a deep understanding about your scenario, please share with me the following info:
- Does this issue happen to all workbooks or particular workbook?
- Can you edit query normally after you set up Excel in safe mode?(Hold CTRL key and click workbook.) If so, that means this issue may be caused by Add-ins. You can open the workbook normally and click File>Options>Add-ins to disable your Add-ins one by one to check which one caused this issue.
- Does this issue still exist if you remove this query and add it again?
- Can you edit query normally when you create a blank workbook and add a query to connect the same database?
Please also share with me the previously and new version number of your Office(File>Account>Product Information), OS(Win+R>type CMD) your previously update channel and the type of your Office 365 subscription(Sign in your account in portal>Click your name>My account>Subscriptions).
Thanks,
Neo