Premium will automatically drop tiers if it is earning less than its cost.
When creating a ticket, what kind of message/error are you seeing? Tickets are opened in the my tickets section of support.ezoic.com.
It does seem that your EPMV is currently decreasing, which would best be handled by our Publisher Success team, as they specialize in this area. If we can get you a ticket with them, they'll likely be the best fit for analyzing your site's revenue.