These steps are from the Release Notes. As you can see, you have to migrate your scheduled tasks in the QEMC.
From QlikView 9
When having IIS and updating from Version 9 to Version 10 the QlikView virtual fol-ders (QlikView, QVAnalyzer, QVAjaxZfc, QVClients, QvPlugin, QVJava and QVPlugin) must either be manually deleted after un-installation or changed to point to the new folders (QlikView, QlikViewDesktop, QVAjaxZfc, QvClients and QvPlugin) after the upgrade is done.
If there is no Publisher license (only a QlikView Server license) and reload tasks have been set up, a manual step is required.
1. After installation, start all QlikView services.
2. Go to the systems tab and select the QlikView Server.
3. Go to the General tab for the QlikView Server
4. Under the heading "Migrate Schedules" you will find a button to migrate the schedules. Note that this will only appear if you have any tasks to migrate and if the Management Service has connection to the QlikView Distribution Service.
To avoid that the uninstall of version 9 removes the .config files, please make a back-up copy of the ones you have modified manually. The most common one is QlikView Distribution Service.exe.config.
After an upgrade, the supervision accounts needs to be added in the QEMC again.
When upgrading from version 9 to version 10 you should restart the [physical] server after the upgrade.
Make sure that you delete temporary Internet files on the computer where you run QEMC/QMC after the upgrade.
Do you have some other QlikView Servers with the same license runnning? Did you install .NET 4 before installing QlikView? What does the Event Viewer says? Note that if you have upgraded, you may be reading from wrong folders the xml and configuration files. Check the folder C:\ProgramData\QlikTech as well.
On one hand, QlikView Server 10 requires .NET 3.5 or starting on SR3, .NET 4 to run without issues. On the other hand, if both Servers have the same license number and this license does not allow clustering, one of the Servers will show "Off Duty" and will not perform any tasks.
Please check the Release Notes as they have a very useful step to step guide to install and update.