Hi Jennifer E Lee,
Welcome to Microsoft Community. Based on your information, we suggest you trying to download the files by clicking the three-dots icon > click
Download

Or clicking the files to open it in Teams > File > Save As.
If you still cannot download files, could you please send us the following information:
- please sign in your account in another device (for example, other user’s PC in which that user can download normally) and see whether you can download well;
- if you are using Teams client, please sign in Teams web app and confirm whether you can download there.
If you have any updates, please kindly share them here. Thanks for your cooperation.
Best Regards,
Ariel