Some QuickBooks Desktop users may be prompted with a message βApplication cannot be started. Contact the application vendor.β See image below.
Solution 1 - Rename Windows local/apps/2.0 folder
1. Completely shut down the Sync Engine.
2. In Windows, navigate to the folder:
c:\users\username\appdata\local\apps\2.0
Note: In the folder address, username will appear as the name of the Windows user (as in our example below).
3. Rename the 2.0 folder (choose a name that makes sense for you).
4. Run the Method Sync Engine. This will recreate the folder you renamed above.
At this point, the sync engine should run properly.
Solution 2 - Disable / Re-enable antivirus
If Solution 1 does not work for you, your antivirus program may be conflicting with the sync engine.
2. Disable your antivirus program.
3. Turn off the Windows Defender Firewall.
Control Panel -> System & Security -> Windows Defender Firewall -> Turn Windows Defender Firewall on or off.
5. Re-enable your antivirus program.
At this point, the sync engine should run properly.