How to fix "admin dashboard is a white Blank page after upgrade wordpress"?
Generally, the issue can be solved by the steps belows.
1. Please locate the and edit the file wp-cache-phase2.php file in your favourite text editor(the file normally reside in "<domain>/wp-content/plugins/wp-cache"(e.g. : domain.com/wp-content/plugins/wp-cache/wp-cache-phase2.php)
2. Locate the wp_cache_ob_end function
3. Then inside that function find the line with: ob_end_clean(); (it should be line 219 or about)
4. Finally replace that line with: ob_end_flush();
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