The plugin does not have a valid header

Error : The plugin does not have a valid header
Solution :
The simple solution is to move plugin files to /plugin root. For example:
/wp-content/plugins/akismet/akismet.php
Move or copy akismet.php to
/wp-content/plugins/akismet.php
Your plugins’ folder will be a messy, but at least missed plugins will come back and work.