Diagnosis
That's the brushless motor protection circuit triggering. It's a thermal or overload error.
How to Fix It
Let the tool cool down completely. Remove the battery. Check the anvil for a seized fastener. If it's stuck, free it before restarting. After cooling, install a fresh, charged battery. Press the trigger. It should run normally.
If That Didn't Work
The problem might be in the battery terminal communication. Clean the gold-plated battery terminals on the tool and the battery with a dry cloth. Re-seat the battery firmly.
Heads Up
Continuous flashing red/green under normal load means a failing motor or switch. That requires a service center.