There are three possible reasons the Add button in the Traverse window on the COGO toolbar is disabled.
The distance and direction units entered do not match the units specified in the Editor Options
The distance and direction units are based on what is set in the Editor Options menu. By default, the direction type is set to Polar coordinates with units of decimal degrees. However, if the directions entered in the Traverse tool are in a different format, such as bearings in units of degrees-minutes-seconds, the Add button is disabled.
To enable the Add button, modify the Editor settings by following the steps below:
Incorrect syntax entered for the direction value
When setting the bearing angles, ensure that hyphens are used to separate the degrees-minutes-seconds values, as opposed to using spaces. As an example, the correct notation for the direction, S 89° 45' 25" W, is S 89-45-25 W, instead of S 89 45 25 W, which is incorrect.
When specifying the quadrant that the bearing lies within, there are two syntax options:
Using the same example as above, insert the angle as 89-45-25-3 since the southwest direction lies in Quadrant 3.
Additionally, when inserting direction values with 60 minutes, such as 89-60-00-3, it is incorrect because 60 minutes makes an hour (degree). Use 89-59-59-3 instead.
An existing line segment is not created prior to using either the Angle-Distance or Tangent Curve course types
When working with the Angle-Distance or Tangent Curve course types, they require an existing line segment to be present within the edit sketch to be calculated from. To create a straight line segment before using either course types when sketching a new traverse, the initial course type used is Distance-Direction. Refer to ArcMap: About creating a line with the Traverse window for more information.