Hello,
yes this can happen.
There are certain “actions” that flush the cache,
‘after_switch_theme’, ‘wp_ajax_edit_theme_plugin_file’, ‘wp_update_nav_menu’, ‘wp_delete_nav_menu’, ‘activated_plugin’, ‘deactivated_plugin’, ‘upgrader_pre_install’
so this is normal behaviour.
Please check after those kind of actions – cache should persist.
C.
Ok. But there were no such actions on my site and page cache is empty now. One minute ago there were 5 pages. It flushes every minute.
Do you have “Admin bar ‘PC Flush’ icon” enabled?
The above hooks result in a flush.
If none of this is happening on your site, there must be another issue.
Is APCu flushed somehow?
You might want to install atec-debug and check for any atec-* related errors.
No Admin bar ‘PC Flush’ icon” is not enabled and APCu is not flushed.
When I click pages they appear in page cache first then disappear.
Can you provide your site name?
Install atec-debug and check for errors?