Not able to change page layout

Problem:​

Due to some problem in page, Page Layout button in ribbon is showing disabled.

Solution:

Use following as QUICK solution if you are creating a new page:

1. Delete newly created page
2. Go to site settings > Page Layouts and Templates
3. Locate "New page defualt settings" and select the page layout that you want to set as default page layout.
4. Save setting
5. Create new page

There can be many reasons of Page Laout showing disabled in ribbon. You can reference following links to go deeper and resolve it properly.

1. Try check out the page and then go to edit mode of the page.
2. Try different browsers to change page layout
3. ​Change page layout using powershell
4. Reference link 1​