The long-stalled Filene’s redevelopment in downtown Boston will resume within days, as the project’s developer has signed the advertising firm Arnold Worldwide to occupy a large chunk of a $630 million complex of new offices, stores, and luxury homes.

The upcoming work will bring life back to the property and accelerate the broader revitalization of Downtown Crossing, where the blight at Filene’s has undermined an otherwise robust period of construction activity in the area.