HELP! thumbnail problem

Hi ,, i know this is not a thesis theme support forum but i am thinking this is not related with the thesis theme .. like related with php or something but i can not figure that error out

i am building a blog on a free host for testing but having general problems in 3-4 hosts

would u check? https://isad.myartsonline.com/wordpress/

in this site thumbnails are not showing .. can not figure out what is the problem .. tried all the things mentioned in f.a.q.