I have a suspicion that New Blog Templates isn't compatible with PHP 7.2.8. With debugging enabled, when I go to my multisite network dashboard, I get the following messages:
Deprecated: Function create_function() is deprecated in /home/inrs/public_html/wp-content/plugins/blogtemplates/blogtemplatesfiles/blog_templates.php on line 37 Warning: Cannot modify header information - headers already sent by (output started at /home/inrs/public_html/wp-content/plugins/blogtemplates/blogtemplatesfiles/blog_templates.php:37) in /home/inrs/public_html/wp-admin/includes/misc.php on line 1126
If I go to the multisite network level > Blog Templates page, I get the two message above, plus the following two:
Notice: screen_icon is deprecated since version 3.8.0 with no alternative available. in /home/inrs/public_html/wp-includes/functions.php on line 3856 Notice: get_screen_icon is deprecated since version 3.8.0 with no alternative available. in /home/inrs/public_html/wp-includes/functions.php on line 3856
If I continue and create a site with Blog Templates anyway, the plugin does work... not sure if it's really an issue or not.