WHO: All users using a Mac 10.10 or 10.11 OS computer or device to access the system
WHAT: Due to changing security requirements, Mac OS 10.10 & 10.11 will no longer be supported for accessing the system. To access the system those devices will need to be upgraded to 10.12 or newer.
You can check which version of Mac OS you're using by going to the Apple menu and selecting, About this Mac.
You will then see the OS version:
WHEN: November 15, 2019
If you need any assistance, please submit a support request.