Background Checks
...the simpler your background the easier it is to check. I was cleared in about two weeks. Now if I was an international business man with business ties all over the world including business ties with folks who were our adversaries in an assortment of places, it would take longer. Kushner hasn't been denied a clearance, it just hasn't been completed.
...once it is completed he still will not be able to run by the whitehouse vault and ask for all the classified material that has come in because he doen't have a Need To Know. If you are not directly or indirectly involved in something, ya don't need to know therefore no secret material will come into your possession.