How do I repair the E6621A measurement application if it fails to launch?

The E6621A application resides on the D: drive, although it is also dependent on driver software on the C: drive. If the application fails, then this may be due to:

A failed upgrade process that has corrupted the contents of one or more FPGA/DSP devices.
Corrupt/missing files from the D: drive application folder.
Corrupt/missing driver software on the C: drive.
Hardware failure.

If the failure is due to a corrupt FPGA/DSP or corrupt/missing application files, then downgrading the software may clear the fault. However, the software downgrade process is integrated into the application software, which may have failed to launch. The following process allows the E6621A to be downgraded to software version 6.1.2.0, even if the application cannot be launched:

Download the application recovery utility: FixE6621A.zip
Extract the zip file to a virus-free USB memory stick.
This will create folders setup.e6621a and patch.e6621a on the USB memory stick.
Insert the USB memory stick into a USB port on the front panel of the E6621A.
Wait several seconds for the operating system to recognize the USB memory stick.
Navigate to the USB memory stick and double-click FixE6621A.
Software version 6.1.2.0 will now be installed.
Wait until the upgrade process is complete.
Remove the USB memory stick.

If downgrading the software to 6.1.2.0 clears the failure, then upgrade it to the required version and verify that the failure has not returned.

If downgrading the software does not clear the failure, then it may be due to corrupt/missing driver software on the C: drive. This can be repaired via the System Software Recovery Procedure.

If you suspect the E6621A has a hardware failure then contact your local Keysight Service Center.