You will need to either find the underlying error in User Interface (via your web brower's DevTools) or in the backend's dspace.logs. Once you have the underlying error, you can send it to this list and we can do our best to help. Since you just installed DSpace, it's highly likely you are hitting one of our common installation issues listed at https://wiki.lyrasis.org/display/DSDOC7x/Installing+DSpace#InstallingDSpace-CommonInstallationIssues So, check there first to see if the error you find is listed there already.