Hi,
I have not any Windows Server 2012 available to duplicate your issue related to Avaya Equinox.
However, it seems that your current Avaya Equinox version 3.0.0.0.147 is not compatible with Windows Server 2012.
Based on the information from the URL below, only Windows 7 and Windows 10 Enterprise 64 bit are compatible with Avaya Equinox 3.0.0.0.147.
https://secureservices.avaya.com/compatibility-matrix/menus/product.xhtml?name=Equinox+Client&version=3.0
So would you please help to check if you can launch Avaya Equinox in another Windows client (Win 7 or Win 10 Enterprise 64 bit)?
Please let me know if you need any further information.

Thanks,
Quang Nguyen

Hi,
Would you please help to provide more information about your Avaya Equinox login issue?
- Your Avaya Equinox version?
- Your Windows client version?
- Have you ever login extension on Avaya Equinox successfully? Or it is failed at the first time?

Thanks,
Quang Nguyen

Hi,
Would you please help to provide more information about your Avaya Equinox login issue?
- Your Avaya Equinox version?
- Your Windows client version?
- Have you ever login extension on Avaya Equinox successfully? Or it is failed at the first time launching Avaya Equinox?

Thanks,
Quang Nguyen