I cannot upgrade Arcserve License from V6 to V6.5 or over on Arcserve menu.
When any underscore "_" is included in domain name or server name of the server using V6, you cannot upgrade it to V6.5 or over. As a solution, you can select either of below options.
1. Change domain name or server name.
2. Use Arcserve UDP V6.5.
Please refer to below page for the details.
https://arcserve.zendesk.com/hc/ja/articles/115003189646 (Japanese only)