Go to “Configuration”.

Go to “System Settings”.

Scroll down to “Sales Setting”.

Tick: Special Price Items cannot be discounted.
Untick: Special Price Items can be discounted.

Click “Save”.

Go to “Configuration”.
Go to “System Settings”.
Scroll down to “Sales Setting”.
Tick: Special Price Items cannot be discounted.
Untick: Special Price Items can be discounted.
Click “Save”.