GoDaddy really lived up to its bad reputation and recently changed their API rules. The rules are simple: either you own 10 (or 50) domains, you pay $20/month, or you don't get the API. I personally didn't get any communication, and this broke my DDNS setup. I am clearly not the only one judging from what I found online. A company this big gating an API behind such a steep price...
So I will repeat what many people said before me (being right): don't. use. GoDaddy.
I thought my API keys were expired, I regenerated them, changed a couple of things, checked all API calls to see if they changed API itself...then I searched the exact error and found out.
For such a breaking change to the API, was it hard to drop an email to every account not meeting the damn "requirements" with an API call performed in the last x months, to alert of the change?