The maximum devices of 4 has been reached for this subscription month

I wonder what devices are meant here. Probably, these are devices (computers, tablets, smartphones) from which you logged in through the cloud.

Actually, I have tacx flux and tacx app, ... where to find the list of devices I do not know. It is really weird because I did not add and additional device. I am using the same gear as I was previous days, weeks, year....  And there is no link to lead you , where you can manage this devices. 

7265855 said:

It is really weird because I did not add and additional device.

Judging by your answer, you mean by devices the equipment that connects to the application. I am inclined to think that it is talking about something else: about those computers, tablets and smartphones on which you launched the Tacx application.

7265855 said:

Maybe, one mac, one iphone....  where is possible to change that?

Probably you cannot change this on your own. I assume that the cloud remembered some four devices on which you launched the application, and now will not allow the application to be launched from the fifth device. You don't need to do anything until you want to use this fifth device. Otherwise, contact support to clear this list of devices.

Probably / unfortunately not. I do not need additional 5th device :) ... cloud somehow registered 4 devices which I  do not use. I have only 2  :)  Support might help me, I hope they will do it quickly.