I’m not sure when this happened, I just noticed it. I have custom taxonomies and post types.
For the longest time I was able to go to domain.com/taxonomy/term and it would display the posts related. Now it’s not.
I’m still able to access it by domain.com/?taxonomy=taxonomyhere&term=termhere
The last time I remember this working I was on Apache but have recently moved over to nginx. I thought I tested a while ago and it and it was working though.
Sometimes a plugin changes WordPress’ internal rewrite rules during an update, an installation or deactivation. If the plugin’s update happens to run after your taxonomy registration it may just wipe out the custom rules for the taxonomy.
To inspect the currently active rewrite rules use the plugin Monkeyman Rewrite Analyzer. See this answer for details.
To refresh the rewrite rules visit the permalink settings page once.