It seems I’m having the same issue and I’m not sure how to resolve it.
I’m using rocketchat 3.16.3 on a URL suffix:
https://mydomain.com/chat I have set my ROOT_URL to https://mydomain.com/chat
Everything works fine except for /api/ecdh_proxy/initEncryptedSession
Here is a short excerpt from the console:
Navigated to https://mydomain.com/chat/_oauth/keycloak?state=eyJsb2dpblN0eWxlIjoicmVkaXJlY3QiLCJjcmVkZW50aWFsVG9rZW4iOiJXN3dkN3l1OFF6M01QS0I4a2dhOVhubmlFYmFlWWFuZGVRTDFFMXRuQU1RIiwiaXNDb3Jkb3ZhIjpmYWxzZSwicmVkaXJlY3RVcmwiOiJodHRwOi8vdGVzdHNlcnZlci9jaGF0L2hvbWUifQ%3D%3D&session_state=7e946e53-9804-44c8-8c49-6e382e7eb167&code=9871a27d-2fc1-4fed-b000-bb5a4a8dbd45.7e946e53-9804-44c8-8c49-6e382e7eb167.58d8e5fc-9929-11eb-9c54-eff7529901fc
Navigated to https://mydomain.com/chat/home
VM322:1 POST https://mydomain.com/api/ecdh_proxy/initEncryptedSession 404 (Not Found)
VM322:1 XHR finished loading: POST "https://mydomain.com/chat/api/v1/method.callAnon/login".
VM322:1 XHR finished loading: GET "https://mydomain.com/chat/sockjs/info?cb=x7n57s6sfe".
VM322:1 XHR finished loading: POST "https://mydomain.com/chat/api/v1/method.callAnon/license%3AisEnterprise".
VM322:1 Fetch failed loading: POST "https://mydomain.com/api/ecdh_proxy/initEncryptedSession".
VM322:1 XHR finished loading: POST "https://mydomain.com/chat/api/v1/method.callAnon/public-settings%3Aget".
VM322:1 XHR finished loading: GET "https://mydomain.com/chat/_timesync".
As you can see it loads all requests from the correct URL except for api/ecdh_proxy/initEncryptedSession. It looks for that one in the root.
This issue only started once I added a custom keycloak OAuth provider.