Can not use the ChatGPT plugin I just paid 19$ for

[pixelman]

Unsupported parameter: 'max_tokens' is not supported with this model. Use 'max_completion_tokens' instead.

means that your code (or plugin) is calling the OpenAI Chat API with an outdated parameter.
The new models (GPT-4.1, GPT-4o, GPT-5, etc.) no longer accept max_tokens —

I use ChatGPT 5 mini
Seems that you need to update the code of the plugin?

[pixelman]

seems an issues with ChatGPT 5 when I choose a ChatGPT 4 it works