As of now, Sovryn is not on Coinbase. There are a variety of reasons why this may be the case, but the most likely one is that Sovryn is not yet a large enough cryptocurrency to be listed on Coinbase.
This is not to say that Sovryn will never be listed on Coinbase, but rather that it is not currently on the exchange.
One thing to keep in mind is that Coinbase has been known to list smaller cryptocurrencies in the past, so Sovryn may eventually be added to the exchange. However, there is no guarantee that this will happen.
For now, those looking to buy or trade Sovryn will need to use a different exchange.