1) Each process needs a slightly different mix of chemicals for colour processing, modern developers like E6/C41/RA4 have eliminated a lot of the very hazardous stuff that was used in earlier processes. However the modern films are designed to use these less hazardous processes, so using the modern chemical sets with an older film, may not give the proper result.
2) Your film is very old, so there could be enough base fog in there that when you reverse process you get black.
3) You are not sure you had the right dilution of RA4 chemicals, this is critical when your experimenting with a process, that you measure everything and keep precise notes, in order to make sure you can repeat the process.
I would take your elderly film and use it for B&W negatives, buy modern film and chemistry for colour film and be done with it.