Can't edit images – showing broken icon when editing

I have been given a wordpress website to manage updates and plugins. On first inspection of the website (shopping) I noticed the images were huge like 4mb – i clicked on one of the image which is visible in the media library and it opens in the editor but the image is now replaced by a small broken image icon – I try to change the size of this image but it just comes back saying “Unable to create new image.”

All images are working in this website none are broken and I can upload more images but just can’t edit them – it appears it is only the editing of the images that is not working.

So I asked the company to give me a backup of the entire website (without the images folder as it wouldn’t fit) to put on my own server hosting – I loaded it on my server added some images and the editor works fine.

I am thinking it is their hosting – but they will not give me access to their hosting account – they want me to tell them and they will then contact the host.

This is the website: https://www.furniturewarehousesale.com.au

I have noticed this: they only have one folder for the images (not broken into months) I know some hosts have a limit – could this be the problem?

I checked the wp-config.php file and the memory is define( ‘WP_MEMORY_LIMIT’, ’64M’ ); should this be bigger?

I checked the functions.php file for white lines and nothing.

Another suggestion is that there is no PHP GD library on the server – but I can’t check this as I can’t access their server.

Any help with this would be greatly appreciated.