Rated 1 out of 5 stars

per Milton H el ago. 25, 2021 ·

Broken on 78.11.0 where the header completely disappears when enabled. Disabling the plugin does restore the header. Previous version worked well

This review is for a previous version of the add-on (2.20). 

per Dillinger (desenvolupador) a set. 17, 2021 ·

If it doesn't show any headers at all, you possibly clicked "Hide Headers".
Try right clicking a message or the message list and select "Show Headers" near the bottom.
There is also a menu item: View > Headers > Show/Hide Headers.