That depends on the operating system.
If you are running Windows XP or older, then I have no suggestion.
If you are running Windows Vista, 7 or 10, then I would suggest uninstalling TurboCAD, rebooting, then re-installing in Administrator mode.
TC Pro Platinum 2019, 2018, 2017, 2016 & 2015 (all with LightWorks & RedSDK) & V21
System: i7-5820K @ 3.30GHz, ASRock X99 Extreme4, 16GB DDR4-2133 RAM, Gigabyte GTX 970, Samsung NVMe SSD 950 (256GB), Windows 7 Pro (64-bit) SP1