Can't establish a secure connection

This is likely caused by an outdated system & according to EveryMac this system fully supports the last version of OS X 10.8 "Mountain Lion." OS X 10.9 "Mavericks", and OS X 10.10 "Yosemite" as well as OS X 10.11 "El Capitan." It is capable of running macOS Sierra (10.12) as well, although it does not support the Auto Unlock feature. This model is capable of running macOS High Sierra (10.13), and it supports HEVC (High-Efficiency Video Coding), but it does not support hardware accelerated HEVC. This model is compatible with the final version of macOS Mojave (10.14) and the final version of macOS Catalina (10.15), as well. It does not support macOS Big Sur (macOS 11) or later versions of the macOS.

It would be best to ensure it is updated fully to OS 10.15 Catalina (Including all security updates for that system) and then to consider using Open Core Legacy Patcher (OCLP) to update the system to at least OS 12.7.6 Monterey. A step by step guide shows you how to do it. Hope that helps.