I have a custom post type 'question' and taxonomy 'question_tag'using Anspress plugin. When visiting a tag page the title is "Example Tag". Desired result: "Questions on Example Tag". How could I achieve this?
You would need to find the archive.php from your parent theme and copy it to your child theme if you haven't already. Rename it to archive-question.php (based on your CPT type above). Then open the php file and look for where it outputs your title. Add "Questions on" in front of the output.
Without seeing your code, this is the most help we can be.