AS726X library

I am using the AS726 breakout board for a simple optical detector system.

The library is included with the line #include “AS726X.h”

When the software is compiled and run on a UNO clone everything is fine.

However when I compile and run on a Teensy 3.6 it runs exactly as expected until the board is powered down, restarting after power down the loaded software just does not work. Do you have any suggestions as to how I can prevent this.

Many thanks in advance