Educational technologies have the potential to expand access to education to a wider range of people, including those currently without access to high-quality learning opportunities. However, this promise is largely unfulfilled (see S. Protopsaltis and S. Baum, "Does online education live up to its promise? A look at the evidence and implications for federal policy," 2019, Center for Educational Policy Evaluation). Although technology can remove some barriers, it can also have the opposite effect, creating new inequalities. This meta-synthesis summarises the main findings from current research that documents both structural and instructional barriers; and proposes research-supported best practices in online course design and instruction in order to promote greater student satisfaction and success.