Just as a note for the future- if your RF loads up vanilla, make sure you're unsubscribed from the old page, or it will not work

If you're encountering problems while trying to play RF (i.e it's crashing or loading vanilla) and entering -opengl in "set launch options", redownloading HOI4, deleting RF's mod files and redownloading it, making sure RF is in your mod preset, verifying your game flies, etc. isn't working for you, please try redownloading the Paradox launcher as a last resort.

(Note: the following instructions can potentially look slightly different depending on your PC you're using, but it should generally work the same)
First of all, enter "add or remove programs" into the search function of your computer (which should be located in the lower-left corner of your monitor), after which you shall then be greeted with something to this effect:
https://cdn.discordapp.com/attachments/536851046706970657/776784082360074250/1.png
Click on it and you should be redirected to a tab like this with another search function:
https://cdn.discordapp.com/attachments/536851046706970657/776782968266031174/2.png
Enter "Paradox Launcher v2" to find the Paradox launcher, then finally click on the program to uninstall and to confirm the removal of the launcher:
https://cdn.discordapp.com/attachments/536851046706970657/776787823449341972/3.png
The launcher will reinstall itself when you relaunch HOI4, at which point RF will then (hopefully) launch properly.
For everyone who encounters the crashing on load-up problem(on Steam), try using -opengl.

How do use -opengl?
First step is to right-click HOI4, and the interface on the right will appear:
https://cdn.discordapp.com/attachments/612325272766906373/748365332380647444/unknown.png
Then, click properties and you'll be greeted with an interface like this:
https://cdn.discordapp.com/attachments/612325272766906373/748365793364017193/unknown.png
Click "set launch options" and you'll see the launch options tab appear with the input bar. From there, just follow the image below and put -opengl. After doing so, press ok. Then load up your game and test if it works.