/list_folder/longpoll not working with CORS

I see this was an issue 5 years ago, but that issue was reported as fixed. However, I am seeing the issue once again. I can call /list_folder no problem, as well as /list_folder/continue as you can see in my network trace below.

However, I cannot call /list_folder/longpoll. The error in the console is the usual CORS error message:

"Access to fetch at 'https://api.dropboxapi.com/2/files/list_folder/longpoll' from origin 'http://localhost:4200' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled."