Does anyone know a clear reason why this error happens?
Or a fix for it?

Thanks!

Increase nuke use skill range

It's already over 3000. I don't think that's the problem.

As the error itself says, the distance between you and your target is too far to cast the spell. So decrease the nuke attack range. At least for me, a solution was putting -1 to the nuke's range. For example 899 for 900 range.

I have also seen the same msg with close range attacks. Just had to move closer to the target in order to use the skill.