A family of Microsoft relational database management systems designed for ease of use.
Hi Tanya,
After we upload attachments to a task in Planner, the uploaded files will be saved into the Documents library of the corresponding group.
Please go to your OneDrive for Business > click Return to classic OneDrive on the lower-left corner > click the corresponding group name under "Groups" > check whether the file is in the Documents library.
Meanwhile, please click the gear icon > Site contents > Recycle bin, check whether the file is there.
Regards,
James