Text replacement not working in Sierra
Apple engineers and Apple support please note and add it to the list of broken features inside Mac OS.
Before Sierra, text replacement synced between iPhone, iPad and iMac seamlessly.
No longer.
Since Sierra, text replacement no longer syncs. Furthermore, you may add all your text replacement inside your iMac keyboard, but when you restart your computer, it will have deleted them all.
Below screenshot example of some of my text replacement shortcuts before restarting my iMac.
Below screenshot of the text replacement window, with nothing saved after my restart.
iMac, macOS Sierra (10.12), iPad Pro, iPhone 6S