I’m not sure if this will help in narrowing things down, but my main file is snips-tool.php in the snips-tool subdirectory of my plugins folder. Currently I have my action hook written (within a class) in the form:
add_action('activate_snips-tool/snips-tool.php', array(&$this, 'activate'));
Other forms tried:
register_activation_hook(__FILE__, array(&$this, 'activate'));
Outside of my class:
register_activation_hook(__FILE__, 'activate');
add_action('activate_snips-tool/snips-tool.php', 'activate');
Please, any help would be very much appreciated.