Coins Withdrawn From Exchange Are Not Appearing

If the address you entered was correct, you should open a support ticket with the exchange after a reasonable period of time. Check the transaction ID in https://siaprimestats.info/navigator to verify.

Web Wallet

Web wallets present unique security challenges and are not recommend. Any cryptocurrency exchange that supports ScPrime will give you ScPrime addresses and allow you to send and receive ScPrime. This is not a “true” web wallet in the sense that the exchange controls the private key and thus ultimately controls your ScPrime.  So as a matter of good practice, of course, the suggestion is only send what you need to, to an exchange and keep the rest in your wallet.

ScPrime on Large Exchanges

Large exchanges have steep listing fees and minimum volume requirements. Being listed on large exchanges is highly requested and will come with time as community support and network use grows.