It should be under the path C:\Program Data\SOLIDWORKS\SOLIDWORKS Corp 2016\lang\English. So make sure you've mapped it correctly.
If it is still missing then download from this post and map the location as suggested: Fixing Diameter Symbol Displaying As MOD-DIAM instead of ø in SOLIDWORKS
Make sure the Options > File Locations > Symbol Library File is pointing to the correct location.
A few weeks back, the Gtol.sys file simply disappeared without trace from my home computer (SW16-SP2). Resetting the registry did not help but running the SolidWorks repair did. If you have to go that route, make sure to run the Copy Settings Wizard first.
Thank you, crisis averted!! It worked as advertised in the explanation and I am back to work now.