I have a problem with dataLists.I create new list but I can't add new element to this list because the button New Element is desabled. I am using I have Alfresco Community v5.2.0 and alvex-3.0-20170502.123755-241.zip
As you are talking about an Alvex component, I believe it would be better to raise an issue in the project's page.
For datalists, I guess you are talking about the alvex-datagrid project, that is available at Datalist New Item button · Issue #9 · ITDSystems/alvex-datagrid · GitHub
And it seems you are not the first one facing this problem.
Check the following issue Datalist New Item button · Issue #9 · ITDSystems/alvex-datagrid · GitHub
Retrieving data ...