A family of Microsoft word processing software products for creating web, email, and print documents.
The behavior described (cannot visibly highlight more than one line, but single words/lines work and other apps are fine) matches known display/driver issues rather than a Word setting problem.
Based on the provided context, the effective fix is to remove the problematic display driver so Word can render selections correctly again:
- Use the display vendor’s cleanup/removal utility (for example, AMD Cleanup Utility if using an AMD GPU) to completely uninstall the current display driver.
- Reboot the system when prompted.
- After reboot, allow Windows Update to install a compatible display driver, or install a current driver from the GPU manufacturer’s site.
- Open Word 2021 again and test selecting multiple lines/paragraphs with mouse and keyboard.
If the issue persists after driver cleanup and reinstall, also ensure Windows and Office are fully updated, as outdated or incompatible device drivers are explicitly called out as a cause of Office display/selection issues.
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