A220 flight crew reported wing anti-ice system failed inflight. Flight crew diverted to avoid icing conditions.

Narrative

Due to winter ops; and per SOP the anti-ice switches were placed on during preflight. We then de-iced at ZZZ. Everything proceeded normally until shortly after takeoff when we received a master warning for the Left Wing A/Ice Fail. We completed the after takeoff checklist which includes turning the anti-ice switches back to auto. Once the wing anti-ice switch was turned to auto the master warning extinguished. We referenced the air synoptic page which showed the left wing anti-ice valve closed but amber. After a discussion; we elected to perform SOP wing anti-ice test above 10;000 feet hoping it would reset the valve. Placing the switch on again triggered the Left Wing A/Ice Fail EICAS and we completed the associated emergency checklist which has you turn the Wing Anti-Ice switch to off and exit/avoid icing conditions. We notified Dispatch through ACARS and began reviewing our options. The WSI (weather app) icing chart showed icing conditions at ZZZ1 and continuing well past our fuel reserves. We contacted dispatch via SATCOM and the decision was made to divert to ZZZ2 that was free of icing conditions. The flight continued uneventfully. A logbook entry was made upon arrival.