SSIS Package Stuck at "Created Execution" Status

I found that this can also happen if a new version of a package no longer has, previously configured, parameters. The only solution I found is to re-create the job-step after updating the Environment Variables' configuration. Somehow the Job seems to 'remember' the no longer existing parameters, and will not actually start the package because it thinks that some parameter-configurations are missing.

In the interest of having an actual answer on this question and having just run into this very frustrating issue myself, the problem lies in package/environment parameters. When a package is run on a schedule, if required package parameters are not supplied, SSIS just... sits there. No errors are reported, but the package never actually starts.

Providing values for the required parameters will resolve this issue.