Hi @RQ1, welcome to the Asana Community Forum! Let’s try to solve this together.
I just tried to reproduce this on my end but I was able to download attachments as usual. I recommend you following these troubleshooting steps that usually solve this type of issues: Asana supported browsers and troubleshooting steps | Product guide • Asana Product Guide. Also, please try to disable any ad blocker or antivirus to test if there is something that is blocking you to download attachments in Asana.
If the issue persists, please contact our support team so we can have a closer look at your account setup: How to contact our Support Team ✉
I hope this helps!