Objectives: The rapid expansion of digital health technologies during and after the COVID-19 pandemic has reshaped how individuals access healthcare services. While these innovations promise greater efficiency and reach, questions remain about their equitable uptake across different population groups. This study investigates the adoption and sustained use of MyHealth, a digital health platform introduced by the Catalan National Health System in 2015 and widely integrated into primary care delivery. Methods: Drawing on longitudinal administrative data covering around 80% of the Catalan population (9.46 million individuals) and over 727 million healthcare records from 2015 to 2023, we analyse patterns of digital engagement using survival analysis and microeconometric modelling. Results: Our findings reveal persistent inequalities in both initial adoption and long-term usage. Engagement is higher among women, Spanish nationals, and individuals from higher-income areas. At the same time, older adults, migrants, and rural residents are significantly less likely to adopt or sustain use of the platform. These disparities were particularly pronounced during the pandemic's peak, when digital health use surged. Concentration indices confirm a clear pro-wealth bias in digital health engagement, challenging the assumption that digitalisation automatically enhances equity. Despite the platform's wide availability and integration into the healthcare system, structural barriers, including digital literacy, cultural and linguistic accessibility, and infrastructure, continue to shape patterns of use. Conclusions: This study presents one of the first comprehensive, large-scale assessments of digital health inequality in Europe. It highlights the need for targeted, evidence-based policies to ensure that digital health transformation supports rather than undermines equity goals in healthcare access and delivery.