What firmware version?
If 5.6.x or 5.7.x you must use MrPI to install packages.
The update button will always be grayed out in the above case.
You can not, and never have been able to, install our signed packages with a re-boot (that leads you to an installer that we don't support).
How about some details beyond: "application can not be started"
Like in, what application?
