Thanks for sharing the additional information @neeraj55rai. From reviewing the details I suspect what may be happening could be related to your WordPress administrator account and the Google accounts used to connect Site Kit.
In order to get Tag Manager successfully connected, have you tried to disconnect the module before connecting once more (Site Kit > Settings > Tag Manager > Edit > Disconnect Tag Manager from Site Kit), or disconnecting your Google account from Site Kit before connecting once more, and then connecting the Tag Manager module?
If you haven’t tried both the above, please go ahead and do so. If the same occurs, or if you already performed these checks, please go ahead and reset Site Kit (Tools > Available Tools > Reset Site Kit). Note that by resetting, you will need to connect all previously connected modules once more. Any other users previously connected, will also have to set up the plugin once more. From reviewing your Site Health information I can see there are 2 connected users.
Let me know if you have any questions with the above.