Have you tried:
-deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s). You can do this with ftp or my using the file manager provided by your host. Rename the plugins folder plugins-old
-switching to the default theme to rule out any theme-specific problems.
Can you check your server’s error logs? A blank white screen usually indicates a fatal PHP error (possibly related to a plugin or theme you’re using on that site).
Add `error_reporting(E_ALL); ini_set(‘display_errors’, 1);
define( ‘WP_DEBUG’, true);` in config.php
IF not work try below
1) Rename plugin folder and check or deactivate all plugin active one by one.
2)If above is not works . Check any space is there end of function.php file
3)If above is not works active default theme
