See attached photo. I pay for the $100/year personal use license from ESRI using google login on my main email. When I go to developers.arcgis.com it says I'm logged into my regular account. So when I go over to my dashboard and click create API, everything looks good until I try to click the create button -- thats where I keep getting this "Error Occurred" message. Do I need to make a whole separate account just to sign up Via the developers.arcgis.com instead of using my normal AGOL account?
You will need to either create a developer account or use an ArcGIS Online account to create an API key on the developer website. The ability to create API keys with a Personal Use account is not supported at this time.