"Missing Configuration in Script" error is given when the extension cannot fill a required field that is added to the listing form recently. This error occurs mostly on Mercari.com.
Why are you getting this error probably?
It has been a long time passed since you added your listing to the platform. The listing platform (Mercari/Poshmark) has added a new required field to the form. Since this new field in your old listing is missing, the PrimeLister Extension cannot auto-fill that field when it is creating a new listing.
How to resolve this error?
When you get "Missing Configuration in Script" error when you try to do a task in a listing, you should edit your listing for once only. During the editing, you will see the missing field when you try to save the listing. Fill this field yourself and save your listing. After this step, you can use PrimeLister Extension again for list posting seamlessly.
If you get a "Platform can not be empty." error, you have to edit the listing and select the platform and save it.