PROBLEMS ASSOCIATING EXTENSIONS

Good Morning;

We have several clients in which we cannot associate extensions to Rainbow users. The central is correctly connected and when we go to the user the extensions appear. But when trying to associate them it gives us an error of:
Cannot read property 'mode' of undifined.
And it won't let us associate it, does anyone know why it gives this error?
We have been with these problems for a few weeks and we cannot get it to go correctly. The strange thing is that they are only customers ...

A greeting;