If the CFD underlying stock is subject to a short sale restriction, then that restriction applies to the CFD as well since these are hedged in the underlying market. See KB1432 for details regarding the Reg. SHO Short Sale Bid test.
Disclaimer: CFDs are complex instruments and come with a high risk of losing money rapidly due to leverage. 57.9% of retail investor accounts lose money when trading CFDs with IBKR. You should consider whether you understand how CFDs work and whether you can afford to take the high risk of losing your money.