Support is free on every plan, including the free plugin. Start with the documentation, because most questions are answered there faster than a reply arrives.
Cost
Free on every plan
First reply
Within 24 hours
Euqin Pro
Goes to the front of the queue
Try the documentation first
Three guides cover almost everything a new install runs into.
Write what happened and what you saw on screen, and a reply arrives within 24 hours.
What happens to the information in this form is covered by the privacy policy.
What support covers
Covered
Euqin doing what the documentation says it does
Installing, activating and configuring the plugin
Anything in the ordering wizard behaving unexpectedly
Orders, emails and statuses not working as described
Moving a Euqin Pro license to a different website
Not covered
Writing custom code for your site
Conflicts caused by other plugins or your theme
Building or redesigning your website
Writing your menu, your descriptions or your photography
Managing your incoming orders for you
When a problem turns out to be one of the second list, we say so plainly rather than going quiet. The Setup Package covers configuration work, and custom development is a separate conversation.