Look carefully at the topic at the link.
There is also a link to a file sharing site where you can find OpenScape Manager V3R10.2
https://www.tek-tips.com/viewthread.cfm?qid=182261...

I already have this installer. When I try to install "OpenStageRNDIS V3 R0.3.1 Install.exe" I get the error "The INF file you selected does not support this method of installation. Operation not allowed in WOW64"...

5.1.10 New in version V3 R1.2.0
o Password Encryption in Microsoft Windows Registry
OpenStage ConnectionService encrypts user password, when stored in Microsoft Windows registry.
o Support of Windows 8 32/64 bit
OpenStage Manager and OpenStage 60/80 T RNDIS Driver support Windows 8 32/64 bit.
o Support of Microsoft Outlook 2013
OpenStage Manager supports the synchronization between Microsoft Outlook 2013 (32 bit only)
and OpenStage telephone.
o Enhancements in Key Configuration Menu of OpenStage Manager (OpenStage SIP
only) The Key Configuration Menu has been enhanced to display and edit properly all
available FPK functions, lables and parameters, which are available for the OpenStage SIP
telephone user.

No newer version is available

My suggestion is to install it either on a Virtual Machine or uninstall and re-install

Updating firmware problem was resolved by changing USB-flash to 4Gb.

Driver compatibility solution not founded...

In last OpenStage Manager V3_R3.10.2 (https://wiki.unify.com/wiki/OpenStage_Manager_Rele...) should be "Fixed problem with RNDIS driver installation on Windows 10 1703". But it doesn't work. By default, Windows tries to use the serial COM driver or the Android ADB Interface driver... Maybe some compatible driver can be used?

Can anyone share the 60T drivers from TAPI Callbridge Collection v2 R3.14.0/R3.15.0?

FAQ
FAQ965-7883: HFA SIP OpenScape OpenStage iSDX Realitis HiPath DX Rolm 9600 Hicom OSB Software Downloads