One priority that you didn't mention in the list of priorities that you've set on your duplicants is "Supply".
You do mention "Farm", but that would only cover turning the compost once the polluted dirt has been delivered - it wouldn't cover delivering the polluted dirt in the first place. Nor would "Storage" and "Tidy" cover delivering polluted dirt to the compost, because the compost isn't a storage container.
However, "Supply" would cover delivering resources to buildings that need to consume them e.g. a compost that wants polluted dirt, and if all of your duplicants have something else at higher priority - "Storage" is the likely culprit, considering the amount of materials digging out a base generates - they'll never get around to supplying polluted dirt to the compost.
So prioritizing "Supply" to be at least as high as "Storage" for at least one duplicant is a thing to try.
Also, you mentioned "Tidy". Did you designate the polluted dirt to be tidied? It's not unusual for base building games to have a rule that prohibits objects designated for one job from being used in another, even if the first job was only to store them somewhere else for later use.
So removing any "Tidy" designations on the polluted dirt is another thing to try.