Hi Joe,
Welcome to the community.
First of all, I would make sure that you have the latest graphics drivers for your system.
DainApp is bundled with the necessary CUDA binaries required for it to run (DAIN uses CUDA 9) so you shouldn't need to install anything extra.
You will want to also double-check the GPU that DainApp has selected for use, I know you said you only have one, but if DainApp has'nt selected it by default that could point to an issue.
For reference, what version of DainApp are you using?
Edit: I've been doing some of my own work and I just came across the same error you've been experiencing.
With further testing, I have narrowed it down to the Experimental Algorithm. For some reason it's not recognizing that the PC has a CUDA enabled GPU. The error occurs before any work is sent to the GPU so its not an issue with RAM spikes. It's not a settings problem either as I have tried toggling Half Precision Float, Don't use PyTorch Benchmark and interpolation multipliers in different combinations with no success.
I would advise avoiding the Experimental Algorithm entirely in 0.41