I suspect this is related to Issues with Reactant unable to find GPU on Colab, but CUDA.jl can - #6 by giordano. Try something like
rm(joinpath(Base.DEPOT_PATH[1], "compiled", "v$(VERSION.major).$(VERSION.minor)", "CUDA_Compiler_jll"); recursive=true, force=true)
using CUDA
CUDA.versioninfo()
Does that solve the issue?