A family of Microsoft word processing software products for creating web, email, and print documents.
If non-Microsoft programs are affected it's a rather clear indication that the cause is not specific to any of the Microsoft products. I'm afraid everything you've done has been in vain.
Please see this existing Answer: Select Text.
If that doesn't provide the remedy the next most likely cause is an Add-in or background process which is affecting the system. Reply in detail if necessary.
You also may benefit from a related Answer describing a variety of other text Selection Techniques which are far more accurate & efficient than dragging even when dragging isn't working: