Did you assemble correctly? Specifically the bubble plate? If backwards it can cause this issue.
This could also be caused by "something" in the water. As if there were chemicals or residue left on newly installed products, glass, etc. You could try this: get two 5g buckets. Fill one with newly mixed salt water. Let the skimmer overflow as much as possible through the drain line into the other 5g bucket. As the water level drops add the new salt water to compensate. This would allow the skimmer to pull out whatever is causing it to go nuts vs continuously recycling in the tank water. This process will take some time but you can spread it out over a day where you plan on being home. Check water loss every couple of hours and replace as needed. Mark the sump so you know where to return the water level to each time.