Welcome to the forum!
Thanks for reporting, specifically for giving an exact human readable error message, “Selected model is at capacity”
Your issue has also been reported in this Discourse topic.
You can discuss Codex-related issues here, but the official place to report them is the OpenAI Codex GitHub Issues.
In doing a quick manual search of the open issues for “model at capacity” find
The noted issue suggest using the Codex slash command /feedback but then goes on to note that it is a connectivity problem local to Australia, the issue was posted two weeks ago and has not received further updates so probably transient.
Another commonality with the other Discourse topic is the use of GPT-5.4 with High.
My recommendation would be to open a New Codex Issue as the OpenAI staff watch that list closer than this forum.
Also check OpenAI status for known system issues that the OpenAI staff have investigated and confirmed are an issue.
Until the OpenAI staff confirm it is in a issue, it will not be noted in the status page so lack of seeing an issue does not mean it is being neglected.
The specific error message “Selected model is at capacity. Please try a different model.” is from Codex, e.g.
An earlier issue from a few months ago used similar reply but gave a time to retry, that is now changed.
Which plan are you using?
- Free
- Go
- Plus
- Pro
- Business
- Enterprise
- Other
https://openai.com/business/chatgpt-pricing/
https://chatgpt.com/pricing/?openaicom_referred=true