Sharepoint 2016 wiki document librabry checkout button is greyed out

as per topic, my wiki document library checkout button is greyed out

1) my required checkout is ticked as yes in library settings

2) my site template is team sites 

3) my site features : SharePoint Server Publishing  is activated

notes here

1) before i turn on custom template in site feature, wiki document library checkout button is working fine
2) after i turn on custom template in site feature, the checkout button is greyed out, please help me to troubleshoot further on this issue, many thank