PHP errors

I am getting the following warnings in query monitor

This appears in the main website

call_user_func_array() expects parameter 1 to be a valid callback, class ‘NFMTA_AddonTag’ does not have a method ‘init’

in

wp-includes/class-wp-hook.php:287
do_action(‘init’)
wp-settings.php:546

and shis second one appears when in the admin area

call_user_func_array() expects parameter 1 to be a valid callback, class ‘NFMTA_AddonTag’ does not have a method ‘admin_init’

in

wp-includes/class-wp-hook.php:287
do_action(‘admin_init’)
wp-admin/admin.php:175

All of the forms appear to work just fine no not sure what is causing the warnings, any help much appreciated