How can I upload an image to these forums?

I tried to upload a PNG to the forums in another thread but got an error message: Sorry, there was an error uploading Screenshot 2024-05-30 124646.png. Please try again.

I tried converting the image to a PNG and WEBP and got the same sort of message.

I tried reducing the filename to a much simpler references.jpg but that made no difference.

I tried uploading via the Upload button on the edit bar (above the text entry box) and using copy/paste, but neither worked.

The image is only 764×609 pixels RGB 8-bits.

I tried searching these forums for upload image but got no results.

Can anyone help?