Please enter the license number and use any numbers and/or letters but do not enter any special characters such as - or * or spaces. The message is trying to stop the entry of any special characters or spaces and several states do have only numbers. Please be sure there are no extra spaces at the beginning or the end.
The driver's license number is an added security measure the IRS and States have put in place for 2016 but for most states your return can be filed and will process without your driver's license number.
For more information, please see FAQ below.