This is a general error, the real error is logged in app/storage/logs with today's date.
This usually means:
* If your system was not installed yet:
- Means permissions of storage folder is not correct.
- Means your system installation has not started
* If your system was installed but suddenly had this issue:
Open the latest log in app/storage/logs, if you couldn't find the issue open a support ticket and we'll help.