You can enable error logging in the settings.
Variable is not an array
That means that in some of actions or a trigger you entered pattern with index. It maybe for instance:...
When you create a workflow and configure actions and triggers, you can specify variables in the trigger and action setting fields. These variables enable you to get and process actual values during the execution of the workflow.
{%PHP_VERSION}
The current PHP version as a string in "major.minor.release[extra]" notation.
{%PHP_MAJOR_VERSION}
The current PHP "major" version as an integer (e.g., int(5) from version "5.2.7-extra"). Available since PHP 5.2.7.
{%PHP_MINOR_VERSION}
The current PHP "minor" version...
Yes, you can create a native WordPress filter by using a workflow. Workflows, generated by the jetFlow.io plugin are extremely fast and a filter can be made in a few minutes without coding knowledge. You get your new filter instantly, having created and enabled the workflow.