SmartPTT Dispatcher is not started on Windows 7 with new updates for Microsoft .Net Framework 4.7.1
Check installed updates on your Windows 7. at Control Panel -> Programs -> Programs and features -> View installed updates.
Find all updates related to Microsoft .Net Framework 4.7.1 and remove them:
right mouse button click -> uninstall.
After you uninstall these updates, restart the PC.
Run SmartPTT Dispatcher. The application should run as usual.