If the CircuitHub software ever interprets your EAGLE files as having 0 layers, even if the PCB viewer is showing you the layers, then you may have not defined your Layers Setup properly in EAGLE.
This will manifest by showing you that your Quote is in progress, without it ever completing. If that happens, go to the Board tab and look at the "Number of layers" field. If this says 0, then this is your problem.
Open EAGLE and edit your PCB. Then go to Edit - Design Rules - Layers tab, and make sure the Setup field is set to something standard. A few examples of standard stackups are
(1*16) 2-layer PCB with the core material in the middle.
(1+2*15+16) 4-layer PCB with a core between the two inner layers and prepreg between the outer layers.
(1*2+15*16) 4-layer PCB with prepreg between the two inner layers and cores between the outer layers.
A lot more information about the EAGLE stackup can be found on their website.