I am going to "About Phone" -> "Software Information" and clicking "Build Number" and am presented with a message saying "No need, developer mode has already been enabled".
However I do not see developer mode anywhere, there is no settings menu entry for it and the search menu for "developer" or "usb debug" brings up nothing. It truly is just not there. I have gone to apps and cleared the cache and data for the settings app but still I'm produced with the same message. I have installed applications that claim to open the developer options, but all "error out" in their own way.
I have tried "Reset Settings" with no luck.
I did turn on developer mode about a year ago to see what it did, so that explains why I'm getting that it is already enabled - but the menu option has gone.
I'm wondering if anyone has hit this issue or has suggestions outside of factory reset? I have been searching online but have not found the solution.