The Serum DEX is a little different from raydium.io and requires that "swaps" and other transactions be settled.
Star Atlas, and other DEXes, can also use serum, in the background, and may to "settle" thee transactions too.
The Serum DEX is here: https://dex.projectserum.com/#/
Your funds should go into your Phantom wallet.
What should I do if the Settle function does not not work in Serum?
Connect to your wallet, and go to the DEX section, and see if there is a Settle button, and "Settle" it.
If that does not work, it may be a different issue. The Serum servers may be overloaded, and/or you may wish to contact Serum's support.