How to convert byte array into a single variable
You can't convert 20 bytes to long. Send it as string of hex values. A byte takes two characters in hex, so you will send a 40 characters string, which can be simply decoded back to bytes.

char str[sizeof(myTID) * 2 + 1];
const char* hex = "0123456789ABCDEF";
for (int i = 0; i &lt; sizeof(myTID); i++) {
  str[i * 2] = hex[(myTID[i] &gt;&gt; 4)];
  str[i * 2 + 1] = hex[(myTID[i] &amp; 0x0F)];
}
str[sizeof(str)] = 0;
Serial.println(str);