Domain properties use DNS. URL-prefix properties support methods such as an HTML file, HTML tag, Google Analytics or Google Tag Manager when their requirements are met. A tag’s presence alone is insufficient.
The HTML-tag method places the supplied verification code in the homepage’s source head. Dynamically injecting that meta tag through GTM is not the same as the official Google Tag Manager container verification method.
GTM verification requires the same Google account, Publish or Admin permission and the correctly installed snippet. Keep the token after verification and assign appropriate access to team members.