Firefox blocking some xhr - Does anyone know why is this happening? (CORS and NS_BINDING_ABORTED)

[phase7]

I've deployed the stack on the cloudformation and web-ui is functional. But some of the functions are not working properly. Sign in is not being registered on site and a spinner is going on constantly. I'm using firefox 85 - 64bit.

Network tab shows that some requests are being blocked. I've looked around and this error is related to caching, but Ctrl-Shift-R is not working, neither clearing cache or anything. The console shows Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://retai-loadb-1bo6n2uclsm47-1985101791.us-east-1.elb.amazonaws.com/carts. (Reason: CORS request did not succeed) is showing in the console, is this related?

I've had someone check from elsewhere and they've reported they can visit the site just fine. It even works in Firefox in my phone! This seems to be a local problem. Can anyone help, please?

[phase7]

I've solved it, please see here solution