Soundly support:
You can search and preview sounds without signing in. Sending sounds requires a Soundly account.
If the sign-in screen appears, sign in with your Soundly account. This applies to both Send and dragging audio out of the extension.
Your account determines which sounds you can send.
If you do not have an account, create a Soundly account.
If an included sound still will not send after sign-in, contact support.