Do you have access to another PC?
If you need to carry out further evaluation you can install the software on a different machine which will give you a further 30 days.
I have had the same issue of needing some more trial time and got the same answer from an Adobe representative -- I would need to download a trial to a different machine. Difficult in my case as I have only 1 laptop at home and work remotely. The other suggestion I was given was to read their documentation about the RH11 features and use that to help make my decision -- but I can't build a case to upgrade from their documentation alone.
I am disappointed that I couldn't be given just another day or two of a trial as that is all I would need to generate a few outputs and see if results I saw during my April trial might have improved in the latest version of their trial for that software. For the April trial, I was not satisfied with how the Responsive HTML 5 output from the RH11 trial was behaving and also was not satisfied with a WebHelp output created from the trial (I had hoped it would address some IE11 issues in WebHelp that I produce in RH9, but the issues were still present in the RH11 Webhelp output). I need a physical example of output that addresses my company's needs and that performs well in order to build a case for upgrading.
If anyone learns of other options or of a policy change in the future to allow additional days for a trial, I would appreciate the info being shared here.