Due to the corona virus pandemic, we were unable to send you our product.
"Due to the corona virus pandemic, we were unable to ship you our product, and would like to offer you our apology. In addition, we would like to offer you a refund, and a digital version of our sound track as a present."
「デジタル音源」が"digital version of our sound track"で合っているのか少し自信が無かったのですが、「音源」そのものは"a sound source"と訳せます。（なので、A digital sound sourceと訳せばいいのかもしれません）
アメリカ合衆国 
