DynDNS Arduino - Not updating the IP

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2 
String ipadsl     = String(20);
String ipadslold  = String(20);
String inString   = String(51);

Go read the documentation on the String class, and tell us why you need to initialize ipadsl to "20". Ditto for the other instances.

There is no reason to be using the String class at all.

What do your (commented out) Serial.print()s tell you is happening?