Hello,
Edit: I just noticed you added the slider shortcode via Ad manager, do not use ad manager for slider code.
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Try adding metaslider shortcode via code editor. (edit post -> Top right 3 dots -> select code editor)
I just tested here https://demo.themonic.com/devsite/11 and it is working fine.
Also try by disabling all plugins to rule out plugin conflict, if it still do not work, you can ask the plugin developer support portal https://wordpress.org/support/plugin/ml-slider/
You can also check by installing default theme and checking slider to rule out theme related issue.