Hi there,
I just fixed the problem.
Here are the steps I took in case somebody else have the same problem at some point.
1.- Edit the WP-Config.php file and turn on Debug to True
2.- I noticed two errors (Database backup plugin and Theme-compact)
3- I deactivated the database plugin (that didn’t solve the problem)
4.- Renamed the wp-includes/theme-compact directory (this finally resolved the issue)