Deleting a message posted in a group chat

In Teams, try hovering over your message or clicking the three dots (...) next to it. You should normally see a Delete option there. If it's missing, your organization's Teams admin may have changed the messaging permissions, or your account may no longer have permission to delete messages. You may want to check with your IT admin to confirm if anything changed.

Hi Steptoe, Wendell,

Thank you for reaching out.

The option to delete a sent message in Microsoft Teams may be unavailable because of the messaging policy currently assigned to your account. Please contact your organization’s IT administrator and ask them to check the Teams messaging policy applied to your user account. They will need to make sure the Delete sent messages setting is enabled in the Microsoft Teams admin center.

Your IT administrator can review this setting under:

1. Sign into Teams admin center > Messaging policies.
2. Go to Users > Manage users.
3. Select your user account, select the Policies tab > Messaging policy assigned to your account.

4. Set Delete sent messages to On, save the policy.

After the administrator changes the policy, it may take some time for the update to apply. Once it takes effect, restart Microsoft Teams and check whether the Delete option appears when you select the three-dot menu next to your message.
In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support  

I hope your issue gets resolved soon. Any updates would be greatly appreciated.