My basic r-attack does not work at all!

It just says: " cannot attack because the target is too far".
My character runs to the enemy and starts attacking on my screen, but only animation works, no damage. For others it just shows that im standing near the enemy.

Anyone know what might cause this? I tried with every class, but it does not work!

So basically animation and everything works on my client, but nothing goes through to the server.

Any tips & advice is appreciated

(Oldschoolko private server, haven't heard anyone else having similar problem)