There are several steps that you can take to troubleshoot any issues you have with editing files in a shared Teams channel:
Check that you are using the latest version of the Microsoft Teams app, as earlier versions may not support channel file edits.
Verify that you are the owner of the file.
Ensure that the file is in the same Team and channel as the conversation in which you want to edit it.
Check your settings for that specific channel to ensure that file editing is enabled.
Confirm that the file type is supported for editing in Teams.
