feel like this will be the tipping point into the recycle bin for rf2, sad to see it go by, -but- LMU can hold the candle!
Honestly I took my own advice and it's actually not that easy to find the many posts on this issue (people tend to post a screenshot, and don't name the thread well). It can be the runtimes (a windows or gpu driver update can mess with them), or can be your system not letting the game start (The fact rF2 files have changed could be a factor). Google "steam attempting to start" and you'll find many possible solutions for many games. But I'd definitely start by reinstalling the 4 runtime packages in the Support folder of rF2.
Ha! Im also taking my same advice I just posted in LMU forum.. when the rig gets you down, go ride your motorcycle! Will look at this tommorow again after i get some more vitamin motorcycle.
Are you using VR with openXR? Ive had this happen a couple of times in the past few months, first time reinstalling those runtimes fixed it (or seemed to at least), next time it didnt and i couldnt find a way to fix it, but it ran using steamVR or screen. A few weeks later i tried launching with openXR again and it just worked *shrug*
Nope, no luck so far. no steam issues (all other games launch fine), in frustration I downloaded a cracked version of rf2 to run my kart content, thats working, so for now im good, will wait till another update fixes it, or as you you, it randomly decides to work again...