Hi All,
Unfortunately, it is very difficult to address issues in DSpace 5 as that version is no longer under support. That codebase is also very old (began in 2015), so it is very possible that the Creative Commons API has been updated in a manner that is no longer compatible with DSpace 5. You could check your logs to see if there is additional information (or errors) logged, but it is possible that the issue is not easily fixable.
Regarding DSpace 7.x though, I can verify that Creative Commons licenses should work well. However, there is one scenario where we are aware that there is a problem. If you have a custom "http.proxy.host" or "http.proxy.port" configured in your dspace.cfg or local.cfg (on the backend), then CC Licenses may not work properly. This is a subset of an open issue regarding these proxy settings at
https://github.com/DSpace/DSpace/issues/8603 That ticket is currently being worked on, and I'm hoping it will be included in an upcoming bug-fix release to 7.6. If that's not the issue you are seeing, then I'd recommend following the troubleshooting guide to look for errors that may be occurring:
https://wiki.lyrasis.org/display/DSPACE/Troubleshoot+an+error#Troubleshootanerror-DSpace7.x(orabove)
Tim