I have received an email from Marriott that I've got anniversary gift (1 free night) but I cannot see it in my profile. Any ideas ?
For free nights, it takes about 24 hours for certificates. It should be listed under your Activity page as per the screenshot below.
However, it sounds like you got a free elite night. It should increase your elite night count by one within 24 hours (not a free night).
Hope that helps.
Retrieving data ...