I'm sure there's a solution for that (as you bought all the DLC I'm assuming not a pirate copy of RS, because that WON'T work, ever), but hang tight; I'm mainly familiar with Mac, others here can help you with PC.
I would encourage you to use the latest version to ensure it all works smoothly. That's about all I can counsel for the moment.
Your other choice to get fast response is to ask on the Discord forum as that's typically more active.
Good luck!