Views fields configuration is not working
Apparently you're not the only one to encounter this issue. Here are some similar situations:


https://www.drupal.org/node/2151785
Views UI doesn&#39;t provide links to expand fieldsets anymore


It appears that no one has found out the solution yet. It doesn't seem to come from jQuery Update or backend theme. However, these advices show up each time:


Make sure that the needed JavaScript file is loaded in the header of the node (collapsible.js)
Perhaps a conflict with another module that would use Views hook. Disable enabled modules one by one and test.


If you find which module interferes with Views or why JS file is not loaded, I think you will make more than one happy people.