HELP!!!! 2.5 yr old colt dead Sperm

Looking for help I have a 2.5 yr old colt. We collected him numerous times when he turned 2 with no living sperm, that vet told me he had not gone through puberty not to worry. Recollected him in Dec same result. Brought him to clinic for them to collect same thing. Morphology is good sperm count is ok not super about 3 billion in a 15ml collection. That vet says nothing he can do. I have tons and tons of breedings sold to this colt. I call a very large well know repo vet they say he may have a blockage and to collect everyday and see if that helps. If not might try Oxy to help with blockage. If nothing then we will test for alkaline levels to see if it’s a full ejaculate etc. Is he a “accumulator” any experience with this? He has not been sick I have owned him since 4 months no steroids etc. We was very sick with pneumonia at 5 months old and was on iv meds for a month but vets say that should not be affecting him now etc. Any help would be MOST APPRECIATED