CORS Issue

I’ve been wracking my brain trying to figure this out with no success. I keep getting the message “The ‘Access-Control-Allow-Origin’ header has a value ‘ https://yourlist.com’ ; that is not equal to the supplied origin. Origin ‘ https://sandbox.domain.org’ ; is therefore not allowed access.” My WordPress install is located at //sandbox.domain.org and my subscriber list is located at //yourlist.com/?p=subscribe&id=2. My server is Nginx powered, and I am using the following CORS in the rewrite rules for //yourlist.com. # # Wide-open CORS config for nginx # location / { if ($request_method = 'OPTIONS') { add_header 'Access-Control-Allow-Origin' '*'; add_header 'Access-Control-Allow-Credentials' 'false' add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS'; # # Custom headers and headers various browsers *should* be OK with but aren't # add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type'; # # Tell client that this pre-flight info is valid for 20 days # add_header 'Access-Control-Max-Age' 1728000; add_header 'Content-Type' 'text/plain charset=UTF-8'; add_header 'Content-Length' 0; return 204; } if ($request_method = 'POST') { add_header 'Access-Control-Allow-Origin' '*'; add_header 'Access-Control-Allow-Credentials' 'false' add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS'; add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type'; } if ($request_method = 'GET') { add_header 'Access-Control-Allow-Origin' '*'; add_header 'Access-Control-Allow-Credentials' 'false' add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS'; add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type'; } } It’s only a wide open CORS for testing purposes. Even with this, I am still having issues. Do you have any suggestions? https://wordpress.org/plugins/sign-me-up/ I was actually having the same issue as someone else was having with it actually going through but the error message occurs anyway. I can fix that with CSS.