I'm getting an error message trying to match Mlife Gold --> Hyatt (I've done this before, with Explorist currently expiring end of February 2019):
We're sorry! We're currently unable to process your request. Please try again later.
Your M life Rewards and World of Hyatt accounts have already been matched.
I saw on DoC the tip to log off Hyatt and try again.. still same error... uh oh...
EDIT TO ADD: no sooner did I post this that I got an email saying welcome to another year of Explorist status... feverishly logged back into my hyatt profile, saw expiration 2/29/2020 and club upgrade awards too... now we will see if it sticks, per stgermainparis above..