Conclusion, I advise to save on PC a directory yuneecOTA version 749 with its app and also the file that I put in attachment (the 748). He alone is able to independently force the H + version down without turning on the ST16S.
If the 750 file is bad or badly installed, the automatic upgrade will not replace it because it sees that it is already in place.
If this case occurs, you must first use this method, downgrade the H + version with the microSD and version 748, CLEAR file TYPHOONHPLUS_C23_C / E_1.0.10_BUILD750_20180824 in the directory yuneecOTA and redo an automatic upgrade by OTA. The order of the tasks is important.
The 748 will be replaced by the 750. Even if the H + is not binder, it does not matter, the files are transmitted by the 5.8 Ghz of the C23.
After, do the bind (see the manual).
If this does not work, it is the file CONTROLLER which is bad or its installation does not know well unrolled. If you made a classic backup android, you will always find this bad file, and to be able to download a new one, you have to downgrade version also the ST16S.
It's a bigger payday.
There you have to do a reset factory from android without backup, install the flight pilot 2 (Yuneec-App-Release.apk version 749) then make a udpate from a microSD on which will be copied the file update.zip and the firmware directory from the file TYPHOONHPLUS_CONTROLLER_1.0.10_BUILD749_20180824 that you have decompressed (thank you Peggy and mbernholdt).
Same operation with the microSD in the C23 and the file 748.
Everyone has dropped version, and we redo an OTA update. If everything works, you have downloaded good files or the installation went well.
If ok, we backup the 750 files also because we know they are reliable.
Hard to go through google translate, I hope I have been clear.
This is a method that I personally tested, after you are grown-ups, it's at your own risk, I'm not Yuneec SAV, I'm just trying to help like a lot of people here.