Hello Homayra,
After testing your site very thoroughly, it looks like the issue is actually because of the folder permissions on /images/easyblog_avatar/ . There's something not right with the folder ownerships on the site as they seem to be owned by the FTP user and not the webserver user. You should contact your hosting provider to check on this as they need to reset the folder ownerships.
A temporary work around which I have done is to set the permissions to 777 on /images/easyblog_avatar/ but this is just a temporary solution so that it is writable. You should contact your web host to check on the folder permissions / ownership