When I run a nested regression, I'm getting the following notes:
note: 1.deprivationquintile dropped because of estimability
note: 1.gmfcs dropped because of estimability
note: 0.epilepsy dropped because of estimability
note: 1.AGEgroup dropped because of estimability
note: 1.sex dropped because of estimability

Why might this be? Can I do anything about this please?

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input int totalR byte(deprivationquintile gmfcs) float epilepsy byte(sex AGEgroup)
 59 . 1 1 1 3
 57 3 1 0 1 4
 75 4 2 1 1 2
 72 4 1 0 1 1
 64 4 2 0 2 3
 85 1 2 1 1 2
 61 . . 1 2 1
 76 5 . 0 1 1
 75 4 5 0 1 4
102 3 4 1 2 3
 61 5 4 1 1 2
 54 1 1 0 2 2
 52 1 5 0 1 1
 60 4 4 0 1 1
 90 3 2 1 2 1
 68 3 4 0 1 2
 51 4 1 1 1 1
 71 4 5 0 2 2
 60 4 4 0 1 2
 73 5 1 0 1 1
 65 1 5 0 1 2
 85 4 4 0 1 2
 71 5 5 1 1 3
 73 1 4 1 2 2
 59 2 2 1 2 3
 72 2 5 0 1 4
 57 4 2 0 2 4
 53 5 1 0 2 2
 77 4 2 0 1 1
 85 3 1 1 2 1
 60 . 1 0 1 1
 61 4 5 0 2 1
 91 1 4 0 1 2
 64 5 4 0 2 1
 62 1 2 1 2 4
 57 1 3 0 1 4
 79 4 1 0 1 4
 71 1 4 1 1 3
 65 2 4 1 1 3
 58 2 4 0 1 2
 83 5 4 1 2 2
 92 3 4 1 1 1
 55 4 1 1 2 1
 61 5 1 0 1 1
 79 5 4 0 1 1
 88 1 1 0 1 3
 57 2 3 0 2 3
 61 3 2 1 1 4
 77 . 3 0 1 1
 87 2 4 0 2 1
 83 4 4 1 1 2
 63 2 4 0 1 1
 68 5 1 0 2 4
 63 3 1 1 1 2
 87 1 4 1 1 2
 52 5 5 0 2 1
 68 2 1 1 1 1
 75 5 4 1 1 3
 51 1 2 0 1 1
 68 5 3 0 1 1
 76 4 4 0 1 3
 80 1 5 0 2 1
 93 2 2 1 1 1
 83 4 2 0 2 4
 59 3 1 1 1 4
 64 3 4 0 1 1
 71 3 1 0 1 4
 55 5 2 1 2 3
 90 2 4 1 1 1
 53 1 1 1 2 3
 70 3 4 0 1 1
 56 4 1 1 1 1
 84 4 5 0 2 1
 66 3 5 0 1 2
 73 2 4 0 2 3
 78 1 1 0 2 1
 70 . 4 0 2 2
 56 5 4 0 2 2
 60 1 4 0 2 1
 65 4 4 1 1 1
 79 4 4 0 1 1
 78 3 4 0 1 2
 33 1 5 0 1 3
 29 5 5 0 2 3
 43 3 2 0 1 1
 50 4 5 1 2 4
 34 5 . 0 2 1
 47 4 3 0 2 1
 50 . 4 1 2 1
 45 4 3 0 2 4
 36 . 5 1 2 1
 49 2 1 1 1 4
 45 1 1 1 1 2
end
Many thanks for your thoughts in advance