Admin pages submenu addition not working

I am trying to add an admin page as sub menu of the first admin page but the changes are not visible after publishing. Please refer to the following attached screenshots:

Page 1 (Top Level Item) - https://paste.pics/PVNYE

Page 2 (Submenu for page 1) - https://paste.pics/PVNYL

After Publishing -

Page 2 is not appearing as submenu for page 1. Toggle icon is also not available.