Trying to help here, but need more info.
This is a typical problem, but causes can be several.
Are you sure Uv mapping is done? The size of the texture wont help if the UV mapping is badly set, so it could be just mapping a small piece of the texture, and that is why it shows so big pixels. Check that the UV mapping is good and correct, first of all. A good uvmapping is absolutely key in texturing. 3D Painting is cool, but a good uvmapping and old school 2d painting and editing, will give a lot of control and precission. I use 3D painting mostly for seams, for organic models, etc. IMHo it's usually a combined method.
Is not clear to me if you see all black or something at low resolution, reading the question... I don't know in Maya, as I don't use it, (but used other packages for years, 3D is similar in the end...) but often the full black can be no actual UV Mapping done, inverted normals (all 3D packages have fast tools to flip or fix them), the UVs are wrong, and the texture has black lines or areas in it, and it's just covering all model with a black part detail (wrong scaled UVs, often).
Some packages will show a black render when you just did not create a material for it. (Again, I only handled Maya in some teams for handling assets, I'm a Max and Blender user, mostly)Or did not asign well the texture, UVs aren't there as I mention, etc. Sometimes simply you have not any lights and for that specific viewing or render, it does not do automatic open gl lighting: needs one light there.
In some packages, in viewport, always low resolution textures are shown, per software preferences, so to get best performance. These days I think this habit is dissapearing. If that happens, is a matter of going to preferences, and put viewport texture resolution a bit higher.
So, summarizing solutions:
- Check your UV mapping.
- Check normals.Flip them and/or fix them, to see if it gets fixed.
- Check how you created the material and asigned the texture.
- Check if it's a lighting matter in the way you are wanting to display/render it.
- Related to all this, might be good to see if at preferences are correct in stuff related to these matters.