То OpenCart users: the OpenCart community has located the reason for the Admin Area login problem where a ‘MySQL server has gone away’ error prevents webmasters from logging into OpenCart. The issue has been traced to an empty currency update file, which is causing the login script to timeout.
So here is how to disable the currency update file from your phpMyAdmin/phpPgAdmin:
1. If your table prefix is oc_, then find oc_setting;
2. Find this line from the table: config_currency_auto;
3. Where the key is: config_currency_auto, change the value from 1 to 0;
NOTE: Тhis is a temporary workaround until an official fix is released.