undefined array key error

I don't see any attachments to your post but I suspect the problem is due to a PHP deprecation (Showkase has not been officially updated in a while and new versions of PHP can cause problems).

I've taken it upon myself to create a patch to keep Showkase up-to-date. I've tested it myself and it allows Showkase to work correctly under new versions of PHP (from PHP 7.1 all the way up to PHP 8.5). I've also fixed a few bugs and updated some internal libraries.

You can find a download link for the patch and full instructions for applying it here: https://showkase.net/forum/viewtopic.php?pid=2368#p2368
Please be sure to apply the patch to Showkase v1.7.6 only. If necessary, instructions for upgrading Showkase can be found here: https://showkase.net/support/upgrade/

I'm hopeful that upgrading Showkase (to v1.7.6) and applying the patch to your Showkase installation (if you've not already done so) will resolve your problem.
However, if you continue to experience difficulties, please post back and I'll try to help further. Thank you.

If you do encounter the error again, then try running Showkase in 'debug mode' to see if any detailed warning or error messages are displayed in the Showkase status bar.
Open your 'showkase/admin/settings/constants.php' file in a plain text editor and change line 12 from:

define('DEBUG', false);

... to:

define('DEBUG', true);

This should hopefully help to track down the exact cause of the problem.