File that is uploaded in a Teams Chat group can only be edited by the person that uploaded it. Everyone else is locked out when they open the document.
Please check if the uploader shared the permission of view and edit documents to other members in your chat group. Go to OneDrive->Shared->Manage Access and try to grant other members access to shared documents.
Besides, if the uploader shared documents link to you, please check the link settings in the following picture:
For more reference about chat files discussion in Microsoft Teams:
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