Access Apps and Custom Web Apps Template Retired
Previously, Microsoft Access users could create Access apps that could be used, edited, and shared on the web by creating a database using the Custom web apps template. As of April 2018, Microsoft has retired the functionality of Access web apps and has stopped offering the template for download. For users who want to be able to access and share their Access databases online, Microsoft is now offering PowerApps to business-, education-, and enterprise-level Office 365 Subscribers. You can read more about the transition on the Microsoft Office Retirement Blog and this Microsoft Office Support page.
Guidelines for Microsoft® Office 2016, Unit 5, Chapter 1 and 2 (pages 311–312, 332)