Well this is strange, indeed. There have been similar reports by other users. It comes out that there are some themes out there that limit the number of menu items that are displayed. They do this presumably in order to “simplify” WordPress’es admin interface and to get rid off of unwanted additions. If you are able to switch to another theme (or convince its author to stop this evil practice) then you are probably done.
Another workarounds would be to access Jazzy Form’s administration directly at yourdomain.com/wp-admin/admin.php?page=jzzf_forms_top
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If you are able (and willing) to edit Jazzy Forms’ code, please locate the following line in jazzy-forms.php
$page = add_menu_page( 'Forms', 'Forms', 8, 'jzzf_forms_top', 'jzzf_forms', null, 30);
Does playing around with other values instead of 30 bring any improvement?