I had similar issue with default Category and find out ‘_expiration-date-taxonomy’ meta field was empty in ‘postmeta’ table.
When in
post-expirator/classes/Facade.class.php
line 249
$taxonomyName = isset( $opts[‘categoryTaxonomy’] ) ? $opts[‘categoryTaxonomy’] : ”;
I replace with
$taxonomyName = isset( $opts[‘categoryTaxonomy’] ) ? $opts[‘categoryTaxonomy’] : ‘category’;
to set default taxonomy it works well.
