This thread was started and marked SOLVED nearly 5 years ago.
Lots of time has passed since this thread was started, so there are potentially new issues, potentially alternate solutions and even possibly new & better instructions for using the same solutions.
However, since this thread was started there have been many different responses bringing up different and unrelated issues.
Given the age of this thread and the multiple topics being discussed within this thread, the best course of action for anyone having an i2c lcd backpack issue that isn't resolved by the information that they read in this thread is to search for a more current thread on the topic (there are MANY) or to start a new thread.
--- bill