Open the channel where you want to restore the Message history tab.

Select the Files tab.

Click Open in SharePoint.

Go to Site Content in the SharePoint site.

Select the Team Message History document library.

Open the folder with the same name as the channel with the missing Message history tab.

Open Messages.aspx.

Copy the URL of the file in the address bar.

Return to your channel in Teams and click on + to add a tab.

Select Website as your tab type.

Name the tab (can be Message history or something else).

Paste the address you copied in step (8) in the URL field.

Click Save.