First thanks for using our Sydney Pro theme!
Please follow the instructions in the below link and enable
WP_DEBUG_LOG in your
With these log options enabled, a more detailed error should be shown. Please share with us the detailed error, so we can discover what’s the exactly reason of the issue.
Before that you can try disable all plugins in your WP installation and keep only the theme active. You can go to the
wp-content/plugins/ folder and rename all plugins to something like
plugin-name_OLD. This way the plugins will be automatically disabled. This way you will have the website working again and the next steps is activate each plugin one by one to identify what’s the plugin causing the issue.
You mentioned that did not found the sydney toolbox plugin in the FTP, then probably you does not have the plugin installed and that’s not the reason of the error.
We hope this helps!
Please try that and let us know the results.