Additional chat-related features and issues within Microsoft Teams for business
As this is a public community forum, I do not have access to your Microsoft 365 tenant and therefore cannot verify the Teams policies assigned to your account. Teams policies are managed in the Teams Admin Center by your organization's administrator.
First, can you please check if you can see the Chat application in https://teams.cloud.microsoft/?
Second, if you are a normal user, please contact your IT administrator and ask them to review the policies assigned to your account in Teams Admin Center > Users > [your account] > Policies, including:
- Teams Messaging Policy to confirm that chat functionality is enabled.
- Teams App Setup Policy to verify that the Chat app is available and not hidden or restricted.
If your organization is using the Global (Org-wide default) Teams policies, your IT administrator can review the configuration in the Teams Admin Center to confirm whether chat functionality is enabled in the Global Messaging Policy and whether any app-related policies could be affecting the visibility of Chat.
Please check and let me know the result.