One of my previous PI ignores requests to share raw data that I generated to other groups. What should I do?

Some years ago, in one of my previous publications where I was first author, we generated datasets that were multiple terabytes each. Back then, my PI told to the journal that we could not easily upload the data in public repositories because of the size, so the paper just says that the dataset is available upon reasonable request.

These data can be actually a gold mine for other groups specialized in data analysis because you can still get a lot of useful impactful information. I think my PI knows it and he wants to keep them for themselves.

I left the lab and moved to a new country, obviously I could not bring the data with me. I was made aware that at least more than 1 research group reached out to him in these years to share the raw data for their own analysis but my PI never replied to the requests.

One of these groups eventually contacted me for help (that’s how I found it out) and I am an advocate for open science so I would be very happy to share the data with them. But I feel powerless. My PI simply ignores these requests no matter who asks. Can my PI do this? Is there a way to politely convince him that it is an ethical thing to share the data? Especially since we got publications out of it. Thank you for the suggestions