not working for me either

It's a "feature" of the aberration map, the regular grapple doesn't work either.

The grapple actually does work, but won't work on any aberration surface. I think (but am not a game dev so can't confirm) this is to encourage the use of items within Aberration, such as the climbing picks or zip lines. The grapple will still work on Dinos, you can grapple the light pets and bring them along (useful for taming the light pets), or you can grapple larger dinos and "zip" to them (useful for grabbing Rock Drake eggs).