Lost my monitoring Index view window!!!!

A blank admin "who's online"/monitoring area after adding mods usually means a template fragment or an admin include got overwritten, or a PHP error is being suppressed. @GaryKing was right to ask for a screenshot, and @SheriffMole's followup shows the problem is recoverable — here is a compact, practical checklist and a couple of safe diagnostic steps to use if this happens again.

• Turn on error reporting temporarily (never on a live site long-term) and check webserver/PHP error logs for parse/fatal errors.
• Compare the mod's admin template files with your backups or the original package and re-upload any missing/corrupted templates.
• Clear phpBB's template cache so the forum recompiles templates (delete compiled files in the cache/ folder but keep index.htm and any .htaccess you rely on).
• Verify file ownership and permissions (typical files 644, directories 755) and re-upload in binary mode if using FTP.
• If the mod added admin PHP files, scan them for accidental whitespace before <?php or after ?> and for syntax errors.

A quick way to see errors while diagnosing (add briefly to a copy of the admin script, then remove it afterward):

ini_set('display_errors', 1);
error_reporting(E_ALL);

Finally: keep one untouched copy of core/phpBB and each mod package, perform mod installs on a test copy first, and document which files you change. That makes it easy to restore a specific template or include instead of doing wide file swaps.