Trouble Communicating With Arduino

Projects General Guidance
2

I would guess it's getting stuck in this while loop:

while (!(b==Serial.readString())){
    }

Try this instead:

while (true) {
  String x =Serial.readString();
  Serial.print("Received <");
  Serial.print(x);
  Serial.println(">");
  if (b == x) break;
}