This paper explains why digital tools that perform well within a single hospital or firm often stall at inter-organizational handoffs in healthcare supply chains. It draws on 12 semi-structured interviews with managers from manufacturers, distributors, providers, and IT integrators in the United States, China, India, and the United Arab Emirates; 10 interviews were retained for comparative analysis. Using thematic coding and cross-case comparison, the analysis identifies recurring boundary conditions, including inconsistent product identifiers, divergent data definitions, and limited partner-level verifiability of upstream events. Adoption progressed when partners created shared master data and code governance, integrated basic data flows to remove duplicate entry, and formalized role-based access and change control. Scaling across sites required standardized identifier rules, label templates, and validated mapping files. Scaling across networks depended on partner-verifiable evidence, including timestamped event logs, conformance testing, staged releases with rollback, and, where appropriate, third-party checks. The paper proposes PRISM-HSC, a phase-by-level model that makes these boundary conditions explicit and supports planning for network-wide adoption in regulated healthcare supply chains. A limitation is that the study relies on a small, interview-driven sample and does not quantify effects or test causality.