A TimThumb error has occured

The following error(s) occured:

The remote file is not a valid image. Mimetype = 'text/html' File = /var/www/html/timthumb/cache/timthumbr2ha2M

Query String : w=210&h=180&zc=1&a=c&src=https://www.glamping.it/uploads/image/1460990561786.jpg
TimThumb version : 2.8.13