I experienced this as well but don’t give up on area 419, they are a fantastic company. That being said the clamp does not fit “all” arca, as some companies such as KRG or RRS have the advertised 1.5” width, the dovetail seems to fluctuate slightly from brand to brand. Unfortunately I had to return the clamp and buy a RRS clamp (luckily found one all the way in Australia). This is something they are no doubt working on and I would highly recommend getting ahold of them to discuss the issue.
As a side note, as somebody who uses a friction style clamp to secure my bipod to my KRG arca rail, I will suggest looking into Area 419’s locking arca rail. I have experienced my bipod moving down the rail after prolonged strings of fire and it can be frustrating at times. After testing the full Area 419 arca lock system, it is significantly better at holding the barricade stop to whatever you connect to it or keeping your bipod in place. I am not sponsored or paid by Area 419, they just had amazing customer service dealing with this same issue with me and most likely paid more in shipping than what I paid for the part as they expedited me another to have to send that one back as well. Sorry you have the same misfortune of a part not fitting as advertised.