If when opening the help documentation in TaxCalc the help windows are blank for all filters then you will need to reinstall the application.
NOTE - There is no need to uninstall the previous installation just re-run the installer from the website.
This may have happened when the program was first installed if the help files did not register correctly during the installation.
If you have a Mac, the article below should help.
Help files not visible on a Mac
If re-installation does not fix the issue then please contact support for further investigation.