Dear @Oakkar Aung,
Good day. Thank you for posting your question in the Microsoft Q&A forum!
According to your description, I understand how frustrating this can be click‑and‑drag text selection is a very basic Word function, and when it suddenly stops working it really disrupts your workflow.
To help me investigate this issue further, could you please confirm the following:
- What version of Office are you using?
- Does this issue also occur in other Office applications (e.g. Excel, PowerPoint)?
- Are you experiencing the same behavior when using Word on the web? Also, are there any other users in your tenant who are encountering the same issue?
- Have you noticed any error messages? If possible, please take a screenshot of the issue you are experiencing and share it with me. This will help me better understand the scenario and provide more accurate assistance.
In the meantime, please try these steps below and check if it works:
1.Check Word’s drag-and-drop setting
- Open Word > File > Options > Go to Advanced
- Under Editing options, make sure “Allow text to be dragged and dropped” is checked
- Click OK, close Word, then reopen it

2.Repair Office Application: You can refer to Repair an Office application - Microsoft Support and then check the result.
Note: Please note that our initial response does not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution.
Please feel free to reply below if you have any update or further concern. Thank you for your valuable time and cooperation. I am looking forward to your response!