Failed cuDNN mnist test Ubuntu 20.04

Hi I have successfully installed cuda 10.2 and cuda toolkit 10.2 (not without a lot of pain) on my machine running Ubuntu 20.04 - see below -

nvcc: NVIDIA ® Cuda compiler driver
Copyright © 2005-2019 NVIDIA Corporation
Built on Wed_Oct_23_19:24:38_PDT_2019
Cuda compilation tools, release 10.2, V10.2.89

I am trying to verify cuDNN installation (I have manually downgraded gcc to 8) through the mnist test but I get the following error:

cudnnGetVersion() : 7605 , CUDNN_VERSION from cudnn.h : 7605 (7.6.5)
Host compiler version : GCC 7.5.0
There are 1 CUDA capable devices on your machine :
device 0 : sms 30 Capabilities 7.5, SmClock 1200.0 Mhz, MemSize (Mb) 5926, MemClock 7001.0 Mhz, Ecc=0, boardGroupID=0
Using device 0

Testing single precision
CUDNN failure
Error: CUDNN_STATUS_INTERNAL_ERROR
mnistCUDNN.cpp:394
Aborting…

Can someone help? (it has already been a nightmare getting until this point :-) ) Thanks!