Hi @AndyHu1
The lsit of file extensions that can be supported by ACC is restricted and you need to request the new file extension to be authorised as public resources. you will need to open a ticket to Adobe Supprot requesting the extension add-ons. Be aware that the extension is case sensitive on ACC's side, so make sure you request the right extension and make sure that files will be provided accordingly, usually extensions are lowercase .avif in our case,
Thanks
Denis