'NexDSButton' does not name a type

Your help please.
I have an ARDUINO DUE card and I am using the NexDualStateButton buttons to be able to program with an NEXTION screen NX8048K070_011C but the problem is that when compiling the following comes up:
'NexDSButton' does not name a type, even using the example that comes in the library (CompDualStateButton).

Please post a link (using the chain links icon on the forum toolbar to make it clickable) to where you downloaded that library from. Or if you installed it using Library Manger (Sketch > Include Library > Manage Libraries in the Arduino IDE or Libraries > Library Manager in the Arduino Web Editor) then say so and state the full name of the library.

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