LONDON — When Europe enacted the world’s toughest online privacy law nearly two years ago, it was heralded as a model to crack down on the invasive, data-hungry practices of the world’s largest technology companies.

Now, the law is struggling to fulfill its promise.

Europe’s rules have been a victim of a lack of enforcement, poor funding, limited staff resources and stalling tactics by the tech companies, according to budget and staffing figures and interviews with government officials. Even some of the law’s biggest supporters are frustrated with how it has worked.

In addition, the response to Covid-19 is raising new questions about the role of privacy safeguards, as digital tools for tracking health and location information, once viewed warily by the European authorities, are now crucial parts of containment strategies.