I’ve become very stuck trying to generate gerber files for an 8 layer board that I’ve designed in Eagle. I previously did a 2 layer board and had no issues getting the gerbers to the fab house I use. This time, when I upload my .zip, I get told by the fab house that they are only seeing 2 layers. Does anyone know of a tutorial for generating gerbers for multi layered boards? Everything that I’ve found is for just 2 layers. I tried using circuits.io (as suggested by my professor) but my file times out when I try to upload. I think I would have the same issue there anyways. It’s probably something simple for a more advanced user but this is only my second PCB. Thanks in advance for any help.
Your second PCB and it’s 8 layer? wow!
Took me years before I was allowed to go beyond 2 
You are checking your Gerbers in GCPrevue aren’t you?
Do so, its free.
AFAIK, open your CAM file and select all the internal layers also.
Save this as a new CAM/ULP file.
8 layers is really impressive for a second PCB.
Well, I haven’t seen any ready made Eagle Gerber Generator files for anything higher than 4 layers.
But what I do know is that you can copy the 4 layer Gerber Gen file and add the other fpur layers. In the additional 4 tabs, You will need to include the dimension layer, the respective trace layer, drill layer, pad layer and mill layers.
Also confirm whether entry level pcb houses can build the board for you before committing to 8 layers. I think good fab houses like wellpcb can get it done. Something ro think about maybe?
All the best!