Issue storing QR in EEPROM and transmitting over RS485

That is the problem with copying someone else's monstrosity. The chances of it working "out of the box" for a beginner is close to zero, because there are too many ways to make fatal mistakes.

To learn this material, start with simple examples from the device libraries and get them working, one at a time. Once you understand each one reasonably well, then start adding the pieces together.