@Peter
Probably this issue may be related to some accitendally deleted files from the registry.
At the link below you find several way to fix this issue.
ugetfix.com/ask/how-to-fix-net-runtime-error-1026-in-windows/
I know that fix it in this way it may take some time so, there is a quick trick that may help you quickly understand if this is the issue.
Try to perform a clean installation of the Install_StarGo_640_SP7.exe on a different PC. In this way you should be able to run the StarGo and Upload the correct firmware.
As a remind we are always available to schedule a remote session to help you solve the issue in the faster way.
@Stephan
Any package includes the complete components set: StarGo.exe, Firmware and Avalon ASCOM Driver.
Is true that an explanation about which version numbers belong together may be helpful for users so we have updated the informations on the download page.
The main difference between the two Firmwares is that the EVO-zero require the motor torque always on immediately on the power on and also after the mount will be parked, in order to work unbalanced.
That's way we keep two different firmware/installer.
Best regards