stevember

It was a compliment, 30 minutes reply on Facebook I was impressed, thank you. Looking forward to updates, and I did purchase it.

I had this same problem, it was doing my head in.

MY SOLUTION
Check the file name to make sure there is no apostrophe in it.

After quite a bit of narrowing down it was definitely your plug-in creating the problem on one of my client sites. Here is the debug information.

Notice: add_submenu_page was called incorrectly. The seventh parameter passed to add_submenu_page() should be an integer representing menu position. Please see Debugging in WordPress for more information. (This message was added in version 5.3.0.) in /home/bushrasl/public_html/wp-includes/functions.php on line 4903

#0 _doing_it_wrong() called at [/home/site/public_html/wp-admin/includes/plugin.php:1385] 
#1 add_submenu_page() called at [/home/site/public_html/wp-admin/includes/plugin.php:1481] 
#2 add_options_page() called at [/home/site/public_html/wp-content/plugins/cookie-bar/cookie-bar.php:16] 
#3 cookie_bar_menu() called at [/home/site/public_html/wp-includes/class-wp-hook.php:288] 
#4 WP_Hook->apply_filters() called at [/home/site/public_html/wp-includes/class-wp-hook.php:312]

Hope that helps.