It looks like it’s a server timeout issue. This seemed to have worked for me:
Open wp-config.php in your sites main directory via FTP (or cPanel)
Scroll to the line which reads:
/* That’s all, stop editing! Happy blogging. */
Add the code above the line:
set_time_limit(60);
/* That’s all, stop editing! Happy blogging. */text
Some hosting companies may not allow you to overwrite this setting from wp-config. However, you can still try.
