Gboard Personal Dictonary not working
It would seem that gboard has a hard time with shortcuts containing punctuation. Ampersands and colons did not work for me, but shortcuts without these characters work fine. A little digging on the web would imply that punctuation in shortcuts used to work in previous versions. I'm not sure if this applies to your situation or not, though.

Gboard 6.2.34 .....
Version = 20170404