While uploading files such as plugins and themes, we will get an error “Unable to create directory /home/username/public_html/wp-content/uploads/2010/10. Is its parent directory writable by the server?”
This is due to changes in server, host or upgrading to new version
Firstly, we need to check the upload file path.
1. Login to wp-admin
2. Click on setting --> media --> "Store upload in this folder"
It will be like /home/username/public_html/wp-content/uploads , change it to wp-contents/upload.
This will fix you issue. If this doesnt fix the issue, you need to check the folder permission. Change the permission of wp-content and uploads to 777 and correct ownership of all the files/folders.