EAX 50 Firmware

Dear Community, 
I participated in a beta test of netgear and received following extender some years ago. 

https://www.downloads.netgear.com/files/GDC/EAX50/EAX50_DS.pdf

When I set it up now I get the issue "ERR_SSL_KEY_USAGE_INCOMPATIBLE" similar to following post:
https://www.reddit.com/r/orbi/comments/1crii99/can_not_access_orbi_configuration_page/

However there is no firmware that I can download for this extender. Any ideas? 
Thanks Nadim