I have some clarifications to add to my previous reply.
This only happens when the new firmware v0.32 is used with an old libiio version.
Can you provide details on what libiio version you are using and what operating system are you testing this on?
If you are working on Linux, then please update libiio to version v0.25, then recompile libiio and libm2k.
If it's Windows, then we need to provide a new installer which is linked to libiio v0.25. We are planning to create a new release of libm2k next week, which will use all the compatible versions of dependencies and will properly work with firmware v0.32.
Once we create a new release, we will also create a new installer for the updated libm2k Matlab bindings.