.htaccess troubleshooting and configuration

I need help troubleshooting and fixing the .htaccess settings and PHP settings on my WordPress Multisite network that is running on a VPS on Centos 7. I keep getting an unspecified alert reading "HTTP error" when I try uploading images to the media library of a subsite that I have created on my multisite network. The images do not load properly, but just load a ghost grey image in place of the intended image. Also, the media library is reporting a Maximum Upload File Size of 63MB when I have specified 256MB in [login to view URL] settings via cPanel. Maximum upload file size: 63 MB.