You should to check httpd error log inside CPanel and check abantecart error log (see menu system/logs on admin side).
Please post more details
these are the errors which i found on abantecart admin dashboard::::
2018-12-21 11:47:11 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 11:47:12 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 11:48:14 - error: AbanteCart core v.1.2.13 Maximum execution time of 30 seconds exceeded in <b>/home/u8214406/public_html/core/helper/html-css-js-minifier.php</b> on line <b>51</b>
2018-12-21 11:50:05 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 11:50:06 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 11:50:44 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 11:50:45 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 11:58:09 - warning: AbanteCart core v.1.2.13 Use of undefined constant CACHE_DRIVER - assumed 'CACHE_DRIVER' (this will throw an Error in a future version of PHP) in <b>/home/u8214406/public_html/core/helper/system_check.php</b> on line <b>126</b>
2018-12-21 11:58:19 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 11:58:20 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 12:08:52 - warning: AbanteCart core v.1.2.13 Use of undefined constant CACHE_DRIVER - assumed 'CACHE_DRIVER' (this will throw an Error in a future version of PHP) in <b>/home/u8214406/public_html/core/helper/system_check.php</b> on line <b>126</b>
2018-12-21 12:18:55 - warning: AbanteCart core v.1.2.13 Use of undefined constant CACHE_DRIVER - assumed 'CACHE_DRIVER' (this will throw an Error in a future version of PHP) in <b>/home/u8214406/public_html/core/helper/system_check.php</b> on line <b>126</b>
2018-12-21 12:22:00 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>
2018-12-21 12:22:01 - warning: AbanteCart core v.1.2.13 set_time_limit() has been disabled for security reasons in <b>/home/u8214406/public_html/admin/controller/responses/common/resource_library.php</b> on line <b>22</b>