Can't use sudo commands after removing the user password

I was searching for a way to disable sudo password promot , then I found a command to remove the user password sudo passwd -d username but after I wrote it and try to make sudo commands it asks for the password, i tried to put the old password and blank password but unfortunately it says Sorry, try again

What should I type or do ?

Problem solved!

I tried to change the password again by passwd without sudo and it didn't ask me for old password then I put a new one.