S2C very low range


I am using an XB24CZ7PIS-004 as coordinator and a XB24CZ7SIT-004 as router.
I did a range test with the XCTU. Outdoor in a line of sight I got a maximal range of 120m -130m (400feet).
Inside my house the range is very short. I have no reception from one floor to the other.

Do you have any idea why the range is that low?

Thank you