Your ID and password should be embedded in the m3u file. You can open it with notepad and check. For example, it should contain a thread like: "....
http://ADDRESS/USERNAME/PASSWORD ..."
I had the same problem with a Samsung 2018 Q7 TV. Reduced the m3u playlist by 90%, now it works fine. Appears to be a TV memory issue, although I don't understand how it happens when the TV is showing 2.6 GB (56%) free memory??