WordPress plugin require_once unexpected

This is a long shot but is there any possibility your text editor is encoding the file in UTF-8 with BOM? Try to save / encode the file in UTF-8 without BOM and see if the issue is gone.

As for your plugin header, while it doesn’t totally follow the recommended format your header should still be parsed correctly since this is what the main code looks like for parsing the header:

preg_match( '/^[ \t\/*#@]*' . preg_quote( $regex, "https://wordpress.stackexchange.com/" ) . ':(.*)$/mi', $file_data, $match )

Notice that you can in fact have spaces / tabs / asterisk at the beginning of each line.

tech