Check the Reliability of Questionnaire using spss

I need to check reliability but i have category variable (nominal/ordinal) .

I choose analyze > scale> put all variable .

my question:
can i use this method for category variables and i have result as follow

Case Processing Summary
N
Cases Valid 6
Excluded 96
Total 102

is there is wrong for the result , why excluded is 96 ?

Reliability Statistics
Cronbach’s Alpha N of Items
.840 36

also, I have 37 variables , one of them is string. that is the reason if n item 36.

I analyze questionnaire and I need slandered example to make my output of analyzing is professional .