110 INT overflowing

I purchased a classic 110INT skimmer about six weeks ago and it has been running great. I did a water change two days ago and now the skimmer won’t stop over flowing. I have adjusted the valve and my water level in the sump is the same as it was before the water change. Nothing at all has changed yet the skimmer just has micro bubbles over flowing non stop and it doesn’t matter what adjustment I set the valve to, it still just over flows constantly. I have turned the skimmer off by unplugging it because I can’t get it to stop over flowing. Please advise.