Hi
unless CumulusMX can pick up data sent from the WH4000SE (=Ecowitt 2320E) with either the Weather Underground (WU) or the Ecowitt protocol with some sort of interceptor (something I don't know), it will not work.
I would recommend you getting yourself a Froggit DP1500 (=Ecowitt GW1000), a little (but very powerful) matchbox size displayless console. Not too expensive - about 50 EUR. (Or if you are not in a hurry and can wait, you can order it in China with Ecowitt for 36 USD).
CumulusMX can pick up the sensor data from that console easily. The GW1000 can also pick up a lot of extra sensors which the WH4000SE cannot display, but you can make them visible in either Ecowitt.net or via CumulusMX (or other application software which can read from the GW1000 API - there are not many, 2 - 3 programs, which can do that, and CumulusMX is one of them).
You might also want to look up the following thread in the WXforum which might be helpful for you (
https://www.wxforum.net/index.php?topic=38206.0) as it deals with the same question asked by someone else, There you can also find a compatibility list of Fine Offset clone sensors (your WH4000SE is such a FO clone console), FO clone consoles and application software. Very instructive. (
https://www.wxforum.net/index.php?topic=40730.0)
We have often CumulusMX related questions asked there. And, by the way, I'm owning a WH4000SE myself - it was my first Weather station and is still operational (even though I have meanwhile extended my sensor "park" - what I then needed the DP1500 (Froggit)/GW1000 (Ecowitt) for).