Ok go into your favorite FTP software or Cpanel (if you got a file manager) and check and see if you got a folder under wp-content __imsgalleries and is there any images in there?
after that go into the WP settings / media and set your Thumbnail size to 250w 160h checkmark Crop and set your medium size 300w x 300h
large size 1024w 1024w for testing
now go to posts menu and add new post click on Upload/insert just above bold button and upload an image and image hopefully uploads click on insert into post and save all changes