I’ve even tried rebooting after changing settings, and frame gen does not seem to enable.
I’m using an RTX 5090, 9800x3D system on latest Nvidia drivers, fullscreen mode and FPS cap set to 165Hz (my display’s max) with G-sync enabled.
Hi! I have the same problem, I updated the game on Steam today and the DLSS frame generation is gone, although in the previous version (dated May 5th) she was there and worked very well. Frame generation is now available in the game only from AMD.
I found a solution to the problem.:
Hardware Acceleration of GPU scheduling (HAGS) has been disabled
For DLSS frame generation to work, hardware acceleration of GPU scheduling must be enabled in Windows settings. To do this:
Press the Win key and type “graphics”, then press Enter.
In the graphics settings that open, find the option “Change default graphics settings”.
Inside this option, activate “Hardware Acceleration of GPU Scheduling”.
Restart your computer.
After that, the DLSS frame generation setting should become available in the game.
its already enabled on mine. DLSS and frame gen setting in game is already available.
The point is when you turn it on its not actually working.
Many people have an overlay on that shows the FPS along with FG if frame gen is on etc.
That doesnt appear to ever go on.
Frame rates do change a bit if u change the quality and native AA / DLAA options but frame generation specifically doesnt appear to ever turn on.
Even the latest nvidia drivers released a week and a bit ago that specifically stated support for conan exhiles enhanced dlss frame gen etc as mentioned above previous version may have been working now its not.
doesn’t work from the start I believe… Just need to activate the ‘smooth motion’ in the CONAN graphics settings, via the NVIDIA graphics control panel. It works but if the in-game framegen worked… We could benefit from both being activated at the same time
Make sure you are pointing the Nvidia drivers at the right executable. One thing I noticed after trying to troubleshoot is that the name has changed for the UE5 executable from ConanSandbox.exe to ConanSandbox-Win64-Shipping.exe. Once I told the drivers (and windows) to look at that executable, my graphics issues settled down.
I have the same issue with FSR framegen.
I can say that DLSS works absolutely flawlessly. My two streaming converter PCs are equipped with an RTX 3080 and an RTX 4060 Ti, respectively. My secondary gaming PC features a 4070Ti, and my main system has an RTX 5090. DLSS works perfectly on all of these GPUs.
Driver Type: Studio
I have no idea what driver you are using (probably Game Ready), but the driver for the 5090 might potentially have a bug. (It certainly wouldn’t be the first time …that this would be the case with Game Ready!) => Try switching the driver type. 
BTW. Also try to disable G-Sync for the 5090:
On the 50-series, this can lead to various errors if you are using a standard G-Sync monitor rather than a G-Sync Pulsar monitor wich is a huge and important diffrence.