Same here - multiple users unable to launch after upgrade to Windows Desktop Client 2.0.8206.0. Tried all steps listed here, same results. If we un-install and install 2.0.8040.0 it works fine until the auto-update.
I get the impression that there may be a multitude of reasons why Spark won't open, but we raised a TAC request to investigate why it was happening on some of our PCs.
In our case, believe it or not, it turned out to be the Wacom pen driver for the pen that came with the laptop. Installing the latest version from Wacom's site (rather than HP that provided the laptop & pen) allowed Spark to finally load.
I understand that certain graphics drivers can also cause this.
You should find a *.dmp crash file at C:\Users\username\AppData\Local\Temp\SparkMemoryDump.dmp which when opened with WinDbg and the .ecxr command entered should show if there was a driver that caused it and which.
In our case it started with:
Unable to load image C:\Windows\System32\ISD_Tablet.dll, Win32 error 0n2
ISD_Tablet.dll being the pen driver from Wacom.
We actually discovered the issue was due to an ADS group policy that prevents .exe files from running in the APPData folder.
We were blocking .exe from running in AppData\Local\*\. However, we allowed .exe to run in AppData\Local\*\*\ so...
versions 2.0.8040.0 and below were executing from \AppData\Local\Programs\Cisco Spark - these worked.
Version 2.0.8206.0 is launched from AppData\Local\CiscoSparkLauncher - this was being blocked.
We enabled the policy and everything works fine.