Sharepoint - Edit/checkout/checkin menu missing or unable to edit documents

1. Click the drop down arrow on the webpart title bar and select
the "modify shared webpart" option. Once the task pane opens, click
the "edit the current view" located just under the select a view
drop down. This will open a new page where you can customize the
view for the webpart. In the columns section, uncheck the "name
(linked to document)" column and check the "name (linked to document
with edit menu)" option.

2. If you have view already configured in your document library the
way that you would like it displayed, simply click the drop down
arrow on your web part and choose "modify shared webpart". Then in
the drop down box that allows you to choose a view to display, just
select the one that you like (instead of the summary view).