This is the shop button code for the 'Spikey' theme by megamoose. This theme only requires you to do one simple edit
Code modifications:Open Themes/spikey/Index.template.phpFind:
// The [calendar]!
if ($context['allow_calendar'])
echo '<td><a href="' . $scripturl . '?action=calendar"><p class="userbarbutton"> '.$txt['calendar24'].' </p></a></td>';
Add after:
//Shop
echo '<td><a href="' . $scripturl . '?action=shop"><p class="userbarbutton"> Shop </p></a></td>';
Then, your shop button should be working