this is my glb file
When the model appears correct in online viewers but dark in your own application, the problem is usually lighting. I don’t know what lighting you’ve set up in the application (models usually don’t provide their own lighting) but this model uses PBR materials and will probably require an environment map.
You can see a similar effect by opening the model in https://gltf-viewer.donmccurdy.com/ and turning on and off the “environment” option.
Apart from possible lighting issue, maybe try using gltf.report and run its script to optimize your GLB file and reduce the number of draw calls and convert all textures to WEBP format.
Here is one possible optimized version of your model, which is also DRACO compressed and has 139 calls as well as less than 1/10th of the file size.
warehouse_1225-v1.zip (7.9 MB)