I tried it on a fresh project and there I was able to successfully apply automatic weights. Here if I try to do it with empty weights I can't select bones in weight paint mode, so that's not an option. I tried searching for answer but couldn't find any. Any help is greatly appreciated :)
I noticed that when I select Armature it highlights all my bones and when I press ctrl + p it seems that the automatic weights is missing as well.
If you're in Object Mode and you hit "a" to select everything, and then hit ctrl + p it shows the automatic weights in the context menu. Hope that helps :)
If it help anyone: I had the same issue but was unable to solve this issue. There was no "automatic weights" in ctrl+p menu nor was I able to assign weights in any other way. After an hour of pain, the issue was that my mesh was disabled for selection. So dont forget to uncheck this option :)
I had the same problem too. When I used Ctrl+mouse click (object data or vertex group) the automatic weight is missing, so the solution is to click on the rig then click the first object, then click the bottom object while holding shift and then when you click Ctrl+P it shows up. I hope that helps.