Unable to guess the MIME type as no guessers are available (have you enabled the php_fileinfo extension?).

if you are using capnel then open cpanel and go to software section then go to F and enable  fileinfo then go to and refresh you page your error will be resolved.

if you are using local server (xampp ) then you will go to php.ini file and change 

;extension=php_fileinfo.dll to extension=php_fileinfo.dll

 

your issues will be resolved after make these changes.