My understanding is that a right of way does not confer that there has to be anything actually on the ground. So the right of way can’t be blocked (either deliberately by a locked gate or a fallen tree etc), but it could just be a field, bog, forest, whatever, there isn’t some standard test like “must be passable by an Austin seven”. The exception to that is bridleways have to be passable by horse.
If it was owned by the LA you might have had a chance of getting something done as it’s a road. Only a chance mind you, they would have to have the complete lack of common sense exhibited by Derbyshire council in ruining byways for everyone by turning them all onto unsealed roads using mostly waste scalpings.
As it’s the landowner, I can’t imagine they’re interested in spending tens of thousands upgrading their farm track if it’s passable to them!