The edge codes are imprinted at the factory. If they don't show up that means that fixer was applied before the latent image was developed, thus removing all the silver bromide before it had a chance to form an image.
That means that either your developer was spent or you accidentally swapped your developer and your fixer.
In the last couple of weeks I have been acting as a lab monitor for the photo teacher at the college where I work. (Free run of the darkroom and free chemistry in exchange for keeping the place clean and keeping the kiddies in line... Sweet deal for me.

) Anyhow, in every group of new students I have met, at least one of them accidentally swaps the fixer and the developer. In this case, I KNOW the developer is good because I mixed the batch myself and I just souped a roll, not an hour earlier. The only other answer is that the chemistry got mixed up.
Anyhow, I know very few people who haven't pulled that stunt at least once but it's also something that most people only ever do
once. (Myself included!)
My solution is to dole out the chemistry I need before I start, keep them in marked containers and always stand the containers in a row in order of use.
In my home darkroom, I have glass measuring cups with handles. I used one of those paint markers to write "D - S - F - H" on each cup. "D" for developer, "S" for stop wash and so on.
In the college darkroom, I have a sheet of peel-off labels with my name printed on them. I stick them on all of my stuff so it doesn't get mixed up with everybody else's. I stick labels on each beaker and I use a Sharpie marker and write "D-S-F-H" on the appropriate label.
Yes, the photo lab is a great place for us O.C.D. people to work!
