Unsupported format image in assistant's play ground

Hello, I have configured my assistant on the platform.
It should be able to analyze the content of an image but when I test it in the playground the image format is not recognized. However, this image is a .png and is recognized in the platform’s chat.

Here is the error message:
Error streaming run: Invalid message content: Expected file type to be a supported format: .jpeg, .jpg, .png, .gif, .webp but got .PNG.

Thanks for your help
Guicel