if you are using the Brave browser, use a not Brave browser.
edit: If you are using brave can you let me know what version you are using? I just tried brave and it works, and old ‘access denied’ + s3 threads in brave’s github discussion area ask users to ‘get the latest version’.
The only time we have seen this is because of the brave browser, not the firefox browser. Having it exist on your HD shouldnt affect firefox. If there are issues maybe the signed link timed out and you need to refresh / try in incognito mode. This is not a reported/known issue and there are many downloads a day going through successfully so you may need to fault find this on your end.