FMAC DMA preload initialization fails with error '1' What should I check?

[KHarb.1]

I have FMAC configured via CubeIDE with the FMAC_PRELOAD DMA request active.The code generated by CubeIDE appears to be identical to what's in the below link except I'm using DMA1 Channel 6 instead of Channel 1:

https://www.st.com/resource/en/product_training/STM32G4-Peripheral-Filter_Math_Accelerator_FMAC.pdf

In code, I run

HAL_DMA_Init(&hdma_fmac_preload)

and it returns 0, but when I run

HAL_FMAC_FilterPreload_DMA(&hfmac,&CTST_IN[0], 18, NULL, 0)

it returns '1'.

CTST_IN is an array of 18 int16_t elements.