Molly I took a look at your earnings report and I notice that your EPMV has fluctuated throughout the months between $4-$7 even back before April. There were a few days you did reach $10 but this wasn't consistent. Not accepting a premium invitation wouldn't affect your EPMV and cause it to drop.
I do see that at the beginning of July that your EPMV did start to drop a bit. This could be due to changes to your site being made such as your theme, ad changes, traffic settings, etc. However, at the beginning of every new quarter, it is also normal to see drops in your EPMV and Revenue.
I do see that you have a Publisher Success Manager who you can reach out to, to help optimize your site for better EPMV. You can contact him within your Dashboard.
In the meantime, you can check out this article on best practices for EPMV. https://support.ezoic.com/kb/article/ezoic-best-practices-for-higher-epmv-earnings