I'm trying to sort the points on the curve using node SORT, but I don't see where the error is, but it just doesn't work. The curve is in motion. Thank you for your help

It's because at frame 53 and afterwards, you have points arcing downwards. You've defined your point order as the distance from location 0,-1, 0 - so those points are now nearer the other ones which are higher in y value.

You will have to devise an equation or some other method for sorting your point numbers - depending on what the entire range of your geometry will be doing.

You can freeze your animation using Timeshift SOP and then copy the point numbers by storing them as an attribute before the Timeshift.