Thank you for reaching out to the Microsoft Q&A Forum. I understand how frustrating this is, when Teams suddenly won’t download files or images from chat.
Please kindly check the Files and links settings in Teams by going to Settings, and make sure the option “Always ask where to save downloaded files” is turned On.
If the issue persists, please try upgrading your Teams application to the Insider version as a workaround.
For more details, please also refer to this following thread with the same issue: MS Teams Free suddenly won't download attachments - Microsoft Q&A
Thank you for your understanding and please feel free to let me know how it goes.
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