I think the problem is you have said you only turned anti-ice on. This should be turned on prior to entering icing conditions, and the de-ice turned on once you receive a master caution for icing.
Icing message will stay until the detector does not detect ice for 5 mins. It should then flash the deice on the MEMO panel. Then once anti-ice and de-ice is deselected, and the icing AOA button is reset (once aircraft clear of residual ice), the aircraft will return to normal conditions.