Every Solana action on OpenSea happens onchain, so you need SOL in your Solana wallet, even to cancel a listing. There are three costs to know about:
The network fee, which is very small and applies to every action.
An account deposit, sometimes called rent, of roughly 0.003 to 0.006 SOL. Solana charges it to keep a new listing or offer account open, and it goes back to whoever paid it when that listing or offer ends. If you paid it, you get it back automatically.
The amount you commit when you make an offer, which is held with the offer until it is canceled, expires, or is accepted.
This applies to every Solana collection, including the ones priced in USDC: the item price is in the listing's currency, and the network fee and the deposit are always paid in SOL. Canceling always costs a network fee in SOL, so keep a little SOL in the wallet even when you are only tidying up old listings.
If your balance is too low, the transaction does not go through. You can swap another token for SOL in your OpenSea wallet, or send SOL from another wallet or an exchange account.