Fatal errors while activating Shopp are typically parse errors. This will often times look something like:
Parse error: syntax error, unexpected '&', expecting T_VARIABLE or '$' in /home/username/public_html/shop/wp-content/plugins/shopp/Shopp.php on line 290
Errors like these normally occur when trying to activate Shopp on web hosting that does not provide PHP version 5.0+. Shopp requires PHP 5.0 (or higher) as it has been designed around new tools and efficiencies introduced in version 5.
The only solution is to upgrade PHP to version 5.0 or higher prior to activating Shopp. Check with your web hosting provider’s technical support for instructions on how to enable PHP 5 support on your website if they provide it. You may need to contact your web hosting provider and request that they upgrade PHP for your website. Some web hosts support both PHP 4 and PHP 5, but PHP 5 support must be enabled manually.