It looks like you’re in a monthly payment plan, have been billed at the end of the month before. Haven’t used any API.
This is the link that shows your current credit balance. Or shows your increasing pending invoice if you are on a monthly bill plan.
https://platform.openai.com/account/billing/overview
If it shows "You’ll be billed at the end of each calendar month for usage during that month." then the only thing that should hold you back is your billing limits, click usage limits there to see if you set a hard limit.
One thing that may stop you is that to some accounts like mine they recently added a different second organization out of the blue. Go to API keys, and at the bottom, make sure your original organization is selected and not a new one with nothing going on.
At the very bottom of the bar you click on your name icon, you’ll get a pop-up where you can switch organizations.