@MegZamani, I have just published v0.0.15 of the lib which should now work (I tested it this time ;-))
Now you will always - even with Serial1
- need a (global) line that looks like this in your code.
USARTSerial& nexSerial = Serial1;
//
// or respectively
//
//#include "Serial4/Serial4.h"
//USARTSerial& nexSerial = Serial4;
//
//#include "Serial4/Serial4.h"
//USARTSerial& nexSerial = Serial5;