When I want to attached the document it shows exclamation mark and uploading file…
Hi @WinnyWelcome to the Atlassian Community.There could be a few reasons why you can't upload attachments and you're seeing the exclamation point.
For further reading see this support article https://support.atlassian.com/trello/docs/adding-attachments-to-cards/
It looks like you're new here. Sign in or register to get started.