There is a common error issued byOpecart > Administrator > System > Error Logs. The problem lays in PHP alocated memory. The error is:
Opencart fatal error allowed memory size of bytes exhausted (tried to allocate bytes)
There are varies suggestions but none seem to work. The primary suggestion is to increase php.ini value:
memory_limit = 64M;
But this seem to have no effect, on both php.ini files (locations: /public_html and /public_html/admin). Instead the solution that worked for usa was to add PHP memory limit into .htaccess. Added the following line that solved the problem.
#increase PHP memory limit in order that Error Log to work
php_value memory_limit 1024M