Textures are not displayed correctly

In Blender, if I map the textures to the objects and render the result, the textures are applied correctly to the objects. If I upload the finished model with the textures to Sketchfab and select the textures in the 3D editor, the textures are displayed as color.
I have not found the error so far and am now looking for help in the forum.

Thanks so far.

Hard to tell without seeing a specific example of the problem, but it sounds like you’re missing UV’s for your model or they aren’t being exported correctly from Blender.

maybe this helps?!

What is UV? How can i fix this problem, that they exported correctly?

Can you show your texture setup in Blender? Note that we don’t support Blender’s procedural textures.

the textures (pbr materials) are from textures.com

What is uv:
https://en.m.wikipedia.org/wiki/UV_mapping#:~:text=UV%20mapping%20is%20the%203D,model’s%20surface%20for%20texture%20mapping.https://en.m.wikipedia.org/wiki/UV_mapping#:~:text=UV%20mapping%20is%20the%203D,model’s%20surface%20for%20texture%20mapping.

From the image you gave us, it looks like you are using multiple materials. Are you sure.you have applied the textures to the correct material?
More about material on Sketchfab here: