Hi,
ImageMagick library is not loaded
No mistery here, your server doesn't have
ImageMagick program installed or if it's installed, they haven't installed required PHP extension
Imagick.
For the other issue, looking at your screenshot, seems like a filesize issue, because there are already two twin images loaded fine (I'd guess this one have a filesize smaller than that that is failing -1,8 MB).
Theoretically you could upload an image up to 6048 KB, but that's PHP, your web server (Apache or other) might be allowing much more less than that.
Ask your hosting or/and try my plugin
Pre-resize Images.
Regards