Error "An Unexpected error has occurred" is seen when clicking on the General settings page. In the localhost logs you might also see a java stack trace that looks similar to:
FTL stack trace ("~" means nesting-related):\
- Failed at: ${i18n.str("system_settings.value.lic... [in template "admin/settings/general/_licenseTable.ftl" in macro "licenseDetails" at line 40, column 29]\
This can be caused by expired license or something in the license folder itself.
To resolve this you will need to clear our all the files in the license folder and restart services.