Air Suspension not airing up all the way

I have a 2001 Volvo that rises to ride height just fine with an unloaded trailer. As soon as I load it I'm riding on my fenders. I drained any water out of the tanks and replaced the air dryer unit while it was in the shop as well as the air levelling valve. Nothing seems to work. I removed the dump signal air line to the levelling valve and there is no air coming to it so the dump valve isn't the issue. Even with the tires riding on the fenders the air bags are still hard but just not enough pressure to lift with load. Is there a priority valve or something I'm missing that would cause the levelling valve to not receive full tank pressure? Thanks

 

Thanks! I plumbed it direct and it still did it. Ended up being 3 air bags that were rusted through on top with pin holes that weren't making noise.