After trying different solutions, I cannot highlight text in Word

Run through the Word-specific troubleshooting steps to identify and remove the cause so that Word no longer needs to be started in admin mode.

1. Test Word without add-ins
   1. Exit Word.
   2. Press Windows key, type Run, press Enter.
   3. In the Run box, type:

            winword /a
      

      and press Enter.
   4. Open a document and test text highlighting.
   If highlighting works with winword /a, the issue is likely caused by an add-in, global template, or a corrupted setting file.
2. Disable COM add-ins
   1. Start Word normally (not as admin).
   2. Go to File > Options > Add-ins.
   3. In the Manage list at the bottom, choose COM Add-ins, then click Go.
   4. Clear the check box for one add-in, click OK, then restart Word and test highlighting.
   5. If the problem persists, repeat step 4, disabling one add-in at a time until highlighting works.
   6. When the problematic add-in is found, leave it disabled or contact its vendor for an update.
3. Reset Word user settings in the registry (damaged options) Back up the registry first as described in the article, then:
   1. Exit all Office programs.
   2. Press Windows key, type regedit, press Enter.
   3. Navigate to the Word Options key for the installed version, for example:
      • Word 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Word\Options
      • Word 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Word\Options
      • Word 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Word\Options
   4. Select Options, then choose File > Export and save the backup (for example, Wddata.reg) to the desktop.
   5. With Options still selected, choose Edit > Delete and confirm.
   6. Close Registry Editor and start Word normally, then test highlighting.
   If Word works correctly, the problem was a damaged Word Options registry key. If not, restore the original key by double-clicking the backup .reg file and proceed to the next methods in the same article if needed.
4. Repair or reinstall Office if needed If none of the above resolves the issue and highlighting only works when Word is run as administrator, perform an Office repair from Windows “Add or Remove Programs” (Maintenance Mode repair). If that still does not fix it, reinstall Office as described in the reset/repair guidance.

These steps remove corrupted settings and problematic add-ins that can interfere with normal text selection so that Word can run in standard user mode with full highlighting functionality.

References:

• How to troubleshoot problems that occur when you start or use Word
• How to reset user options and registry settings in Word
• I can't highlight with my mouse cursor in word documents - Microsoft Q&A
• Cursor no longer working on Mac to highlight text in Word - Microsoft Q&A