Dear Sim,
Good day! Thank you for contacting the Microsoft Community. We are here to assist you.
To better understand the issue, you are experiencing with Microsoft Teams, we kindly request some additional information.
Could you please provide the following details:
- Could you please try to upload the file suing https://teams.microsoft.com/?
- Do you have the necessary permissions to upload files to this channel?
- Have there been any recent changes to your Teams setup or your device that might have caused this issue?
- Have you tried uploading files directly to SharePoint or OneDrive and then linking them in Teams?
- Can you upload files to other channels or teams without any issues?
Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. If it possible please provide complete screenshot.
Have a great day and take care! 😊
Sincerely,
Naren | Microsoft Community Moderator