This problem may appear on installations with enabled Stock filter variations support setting. The variations’ filtration relies on built-in WooCommerce lookup tables. If there are any delays in the lookup tables updates, the filters will continue displaying old information.
We usually recommend to turn on the Direct updates option of the WooCommerce > Settings > Products > Advanced admin tab, but unfortunately sometimes the lookup tables’ update delays may happen even with the Direct Updates option enabled. The workaround includes 2 steps:
- Go to WooCommerce > Status > Tools and press the “Regenerate” buttons for the product lookup tables and the product attributes lookup table. Make sure that the regeneration has been completed in WooCommerce > Status > Scheduled Actions.
- Go to annasta Filters > Plugin settings and press the Clear filters cache button at the bottom of the page (supported starting with version 1.8.1).