In 2015 Marriott announced that it will buy SPG. Beginning with August 18, 2018, Marriott started to merge their websites, apps and loyalty programs. Besides SPG, Marriott will also merge the Ritz Carlton into the same system and all will be on one central website and app.
When you log in to your SPG account you will be prompted with a new 9-digit account number. Since the announcement, Marriott gave you the option to link your SPG and Marriott account to match your status and transfer points between the two programs.
The merging of the IT infrastructure is still going on and there are still system outages and glitches on the website, app and with the backend-systems at the reservation hotlines. Marriott set up a website which will give you an overview of ongoing issues and you can even report your own issues if they are different from the once on the status page.