Server software connects to the Cloud as a client, the same applies for ESDR3 client instance, it also connects to the Cloud as a client. So, as a result, you don't have to open certain ports for them, they operate as outgoing connections, not incoming. Server-Cloud-Client exchange all required info as IP, UUID, etc. automatically, there is no need to manually enter anything.
Do not change the port of SS2DX in ESDR2/3, it's not necessary.
Make sure that ESDR3 detects and works with the SS2DX on a PC with a Server SW.
Please make a screenshot of the working ESDR3 with waterfall.