53 assets available but can't download image without extra costs

Those assets are Premium assets, and they are not included in your subscription. Depending on your subscription, you can get a reduction on the asset price, however. Or you can buy credit packs.

https://stock.adobe.com/plans

By scrolling down, you see what you can buy with credit packs. As credit packs have a higher value, they won't be used for standard assets, as long as subscription credits are available.