How to fix theme Preview is currently unavailable My Theme Custom (Modified) in Blogspot

1. Go to settings >>>>> Basic

2. Add another email by click on Add Authors

3. Open your email and accept the invitation

4. Go back to settings >>>> basic. Make the added email as an admin

5. Remove the first email. The email that you used to sign in blogspot (The first email used)

6. You get notification "You are not an author on any blog yet, create one now to start posting!"

7. Sign in blogspot with added email (the email that added and make as an admin) by using another browser. 

If you were using chrome, sign in internet explorer, mozilla Firefox, Microsoft Edge or Operamini

Method 2

Method 3

3 Ways to fix theme Preview is currently unavailable: My Theme Custom (Modified)