frankym,
I'm not assuming you don't understand how the accumulator works, but I want to be sure we are seeing it the same way. Inside the accumulator is a piston like device with a trapped pocket of air on one side and
oil that is plumbed into the engine
oil system on the other. When the engine is running and the accumulator valve is open, the pressurized
oil will push into the accumulator, moving the piston toward the air side until the pressure on the compressed air side matches the pressure of the running engine. If the oil pressure rises (e.g., higher RPM), more oil will be forced into the accumulator until the air pressure matches the new higher oil pressure. If the oil pressure drops (e.g., lower RPM or heavy braking sloshes oil away from the pickup) the higher pressure air will force the piston out, pushing oil back toward the engine's oil system.
When you initially install and prep the accumulator, the goal is to add just the right amount of air to the air side. If you put in too little air, the accumulator will hold a lot of oil, but it will only be able to push a little of it back out before the air pressure drops so low it can't push any more. If you put too much air in, the accumulator will only take a little oil before the air pressure gets so high no more oil can enter.
If you put 60 PSI of air into the empty accumulator (engine off and valve open), it pushed the piston all the way out. The only way oil can get back into the accumulator is for the engine oil pressure to exceed 60 PSI. Unless your engine oil pressure is a lot higher than 60 PSI, there is likely very little oil in your accumulator for the air to push back out. I suggest you look up the instructions for setting up a new accumulator and reset yours to match those instructions.
The last matter is why your accumulator earlier provided less pressure than you were used to seeing. Keep in mind that the accumulator will match the pressure in your oil system at the moment the valve is closed. Perhaps you had been in the habit of closing the valve when the oil pressure was higher, and later closed the valve when it was lower.
If resetting the air pressure to the manufacturers specs doesn't solve the problem, then it is possible you have one of the other problems you mentioned. Let us know how it works.