There could be a couple reasons why this command is grayed out.

• Make sure you have Surfer 7 (or higher) installed on your computer. This command will not work with Surfer 6 or earlier.
• This command will also be grayed out if you are in Didger 2 or 3 and have a raster project which only contains a calibrated bitmap and no digitized objects. In this case, the command will be grayed out since there are no objects to export to Surfer.
• You will need to have the same bitness of both Surfer and Grapher installed. If you have Didger 4, which is 32-bit, you will need to also have the 32-bit version of Surfer installed. If you have the 64-bit version of Didger 5 installed, you will need to have the 64-bit version of Surfer installed. 
• Verify that you have run both Didger and Surfer as administrators so their paths are written to the registry and they are able to find one another.
• If you have Surfer 10 and Didger 4, and you uninstalled any previous versions Surfer before installing Surfer 10, Didger 4 is looking for a registry key that Surfer 10 does not write. The fix for this is described in detail here: https://support.goldensoftware.com/hc/en-us/articles/226507987-Tools-Surfer-Create-Base-Map-Commands-Grayed-Out-in-Didger. 

Updated September 5, 2018