Permission issue using Transmission on USB HD

I have a Raspberry 5, 8Gb, SD 128Gb.
I plugged in a 1Tb USB HDD, formatted ext4, and gave it full permission.
I installed Transmission on CasaOS, I directed the saved files to the USB HD, but it appears that I don’t have permission to save the files on it, if I save them on the SD it works normally.
What could be happening, could anyone help me?