The outage affected services in both directions between London St Pancras International and Paris Gare du Nord, with passengers unable to clear passport control for around four hours.
The Home Office on Thursday evening claimed the issue had been resolved, adding work was under way to fully restore services. Eurostar has apologised for the disruption.
It follows a national eGate failure on Tuesday 7 May, which impacted arrivals at all major UK airports and saw Border Force officials resort to processing passengers manually.
