The below details will depend on Site/Country, contact your reseller to confirm your on-site setup
Below are diagrams of current standard setup for Smartalock controllers. These should give you a good idea of which devices connect where, and what modules to check while troubleshooting. pdf version available here. Screenshots below
Lockers and controller appearing offline on admin portal
Possible Issues:
Power Issue (Controller is not powered)
Network Issue (Controller is powered but not connected to network)