I have green and gold mums. I particularly like this one because the leaves are edged in white whereas normally, mum leaves are pretty boring. I do have acid soil here.
Do they have to have complete full sun to bloom?
Any ideas would be greatly appreciated.

Does it get at least six hours of full sun?

Check your sunlight. Mine didn't bloom because I planted them under a gas lamp. Another group got light from the streetlight at night. It was like sunlight to the mums 24/7.

Right, they need at least 12 hours of darkness as well as enough sun during the day to bloom.

I never thought of the amount of darkness factor! Makes sense!

That's what they say but I have two street lights and mine still bloom. Go figure.

Are you certain that it is a garden mum and not a florists mum? If I plants a florists mum here they often do not bloom before late in the season and most often freeze.