i gave you that page link in my post and i told you how to fix it.
this is what the config page should look like for gemini-3.1-pro-preview:
model url = https://generativelanguage.googleapis.com/v1beta/models/gemini-3.1-pro-preview
for image generation, you need to use model gemini-3.1-flash-image-preview - configure a new gemini model:
model url = https://generativelanguage.googleapis.com/v1beta/models/gemini-3.1-flash-image-preview