Hi there @margyly, I apologize for the delay in response.
I understand it has been some time since you posted this question but I want to help if you are still facing this challenge or if someone else experiences it down the road.
If you are experiencing this when running local host through chrome, there was once an issue within the Chrome browser that would throw the No ‘Access-Control-Allow-Origin’ header is present on the requested resource but that has since been resolved.
We’ve also seen this type of issue in the past here in Community.
As always please double check your dashboard to insure you have all the corresponding routes correct.
Please let me know if you have any additional questions that I can assist with on this front.