Most likely there is an issue with the .lua file.
First of all, make sure all the textures AND the numbers are in the skin folder. Then open the .lua file and make sure the skin file names in the .lua file matches the actual file names exactly.
Then, make sure the files that are contained in the skin folder are set to false, all others should be set to true.
So as an example:
{"F18C_BORT_NUMBER_NOSE_L_100", 0 ,"your_SKIN_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_L_100", ROUGHNESS_METALLIC ,"F18C_1_DIF_RoughMet",true};
{"F18C_BORT_NUMBER_NOSE_L_100", DECAL ,"your_NUMBERS_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_L_10", 0 ,"your_SKIN_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_L_10", ROUGHNESS_METALLIC ,"F18C_1_DIF_RoughMet",true};
{"F18C_BORT_NUMBER_NOSE_L_10", DECAL ,"your_NUMBERS_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_L_01", 0 ,"your_SKIN_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_L_01", ROUGHNESS_METALLIC ,"F18C_1_DIF_RoughMet",true};
{"F18C_BORT_NUMBER_NOSE_L_01", DECAL ,"your_NUMBERS_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_R_100", 0 ,"your_SKIN_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_R_100", ROUGHNESS_METALLIC ,"F18C_1_DIF_RoughMet",true};
{"F18C_BORT_NUMBER_NOSE_R_100", DECAL ,"your_NUMBERS_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_R_10", 0 ,"your_SKIN_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_R_10", ROUGHNESS_METALLIC ,"F18C_1_DIF_RoughMet",true};
{"F18C_BORT_NUMBER_NOSE_R_10", DECAL ,"your_NUMBERS_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_R_01", 0 ,"your_SKIN_file_name_here",false};
{"F18C_BORT_NUMBER_NOSE_R_01", ROUGHNESS_METALLIC ,"F18C_1_DIF_RoughMet",true};
{"F18C_BORT_NUMBER_NOSE_R_01", DECAL ,"your_NUMBERS_file_name_here",false};
First line tells it how to find the texture (false means it's within the same folder as the .lua file)
Second line tell it how to find the diffuse texture (I think) (true means it's outside of the folder that the .lua is in)
Third line tells it how to find the numbers file
NOSE_L/R_100/10/01 means left and right side of the nose 100s, 10s, and 1s places for the bort number.
This example covers only the nose section, there should be more for the wings and tail numbers, but those are handled in the same way.
Also, if you don't want bort numbers, type "empty" instead of "your_NUMBERS_file_name_here" and then set it to true.
I hope this helps, I know I had a hard time with it when I started making custom skins :thumbup: