You may be trying to move users from one Lync pool to another, but you keep getting the following error when Quick Connect tries to update the RegistrarPool:
A parameter cannot be found that matches parameter name 'RegistrarPool'.
This is a product defect (TF00354601). The changes in Lync are not replicated within the delta sync but only during full sync.
This Product defect (TF00354601) has been fixed in version 5.5.0, see defect ID referenced on the release notes for more information.