Hi! I’ve the same problem.
I’ve just install the plugin, but it gave me that error when I try to insert a mail in the newsletter,
the error log:
18-05-2017 15:45:23 – ERROR – m: 22,9 MB, u: 0 – Table ‘martagelmi_database.wp_newsletter’ doesn’t exist
18-05-2017 15:45:35 – ERROR – m: 22,9 MB, u: 0 – Table ‘martagelmi_database.wp_newsletter’ doesn’t exist
18-05-2017 15:48:43 – ERROR – m: 22,9 MB, u: 0 – Table ‘martagelmi_database.wp_newsletter’ doesn’t exist