HTTP Error Uploading and Uploads Greyed Out

There is an extensive thread here with several workarounds: https://ww.wp.xz.cn/support/topic/http-error-when-uploading-images-17/

It’s my understanding that WP 4.5 does so much more processing with images and especially on shared hosting, it’s creating problems. There are two distinct workarounds that many have had success with. I tried the htaccess method and it solved the problem for me.

1) Add this to your .htaccess file at the root of your WordPress installation just before the # BEGIN WordPress line:

SetEnv MAGICK_THREAD_LIMIT 1

OR

2) add this to your themes functions.php file (actually add to a child theme functions.php file or use a plugin like Code Snippets )

add_filter( 'wp_image_editors', 'change_graphic_lib' );

function change_graphic_lib($array) {
return array( 'WP_Image_Editor_GD', 'WP_Image_Editor_Imagick' );
}

If neither of these works for you, try reading the thread mentioned at the top to see what others have done.