Unsupported access to an object

I'm trying to change a drive's home offset via SDO (can't be done via PDO). Executing the command 'ethercat download -p2 -t int32 0x607C 0' returns "SDO transfer aborted with code 0x06010000: unsupported access to an object"

Obviously it doesn't work. Why doesn't it work?

Everything I've found online simply parrots the failure code and doesn't say why.

From the ethercat docs it looks like i should work. However I always use this syntax
ethercat -p 2 download 0x607c 0 0.
Actually what I always do first is to see which values the sdo has
ethercat -p 2 upload 0x607c 0
0x00000000 0
And then do the download.
ethercat -p 2 download 0x607c 0 1
to set it to 1.

That did it. I didn't specify a subindex, since the drive manual said there isn't one for 0x607C. However, at least in this case, ethercat download doesn't work without it.

'ethercat download -p2 -t int32 0x607C 0 35951' works as expected.