Yeah, a plastic smell on a new unit is pretty standard and usually harmless. It's just residue from the manufacturing process burning off.
Fix: You need to do a test run to burn it off. Make sure the basket is empty. Plug it in, tap the FRY function, and just let it run at the default 195°C for 10 minutes. When it beeps and shows "End," let it cool down completely. That should take care of the smell.
If that didn't work: If the plastic smell is still strong after a couple of test runs, then it's not normal lingering odor. In that case, stop using it and contact Cosori Customer Support. The appliance shouldn't have a persistent chemical smell.
Heads up: While it's doing its test run, make sure you have good ventilation—leave that 5 inches of space behind and above it clear. And remember, white smoke during this process is normal; dark smoke is not.