@kugae.
Thank you for downloading and using my plugin and to reort the issue that you are having.
Whilst I can describe what is happening for you to get this error message, I’ll meed a little more information to get it resolved.
Version 1.1 introduced the facility for calculating the term post counts for statuses other than published for taxonomies created by this plugin.
Version 2.0 extended this to other public taxonomies, e.g. the WordPress-delivered taxonomy “Category” or taxonomies created by other plugins.
The place where you are getting this message is where it is trying to modify the properties for the external texonomy to implement this – and it can’t find the taxonomy.
Now given that the taxonomy name stored in the options comes from taxonomies on your site and the message occurs because it cannot find a taxonomy, this can occur if the external taxonomy used is from another plugin and either a) the plugin has been inactivated; or b) my plugin is trying to modify it before the external plugin has registered the taxonomy, i.e. is a timing issue.
I would be grateful if you could confirm if this is what you have been trying to configure.
Regards,
Neil James