A while back I wanted to change my blog design and found my template designer was not working anymore. I thought I had broken it by editing the html and css. So I started from scratch and installed a standard blogger template but found it was still not responding.
I googled this and googled it some more and found many more bloggers having the same problem but no fix. This drove me up the wall for a couple of weeks until I finally found the solution. It seems there is a bug in Blogger. When you disable the mobile template, like I did, it breaks the template designer. Simply turning it back on will not do the trick, you will also have to restore your template. I’m not sure this will work for everyone but here’s how I fixed it.
Solution: broken blogger template designer
1. Login to the blogger dashboard
2. Before you start make a full back up of your blog
3. Go to Template and click on the icon below Mobile
4. Select: Yes. Show mobile template on mobile devices. And save
5. Go to Template > Backup/Restore (in the right top corner)
6. Click on download full template > save file > ok
7. In the same popup window click Browse and upload the .xml template you just saved
8. Click on customize to go to the template designer, it should be working again