My account merge/combine worked just fine at 1:15pm pacific time today.
It did involve some steps and confusion.
End result, total nights are correct. Total points are correct. Current Status is correct. Reservations are showing up (only Marriott as I had no future SPG reservations)
I wanted to keep my Marriott number and not have to remember a new SPG # so I did the merge from the Marriott site.

These steps worked for me. I’m sure there’s a less involved way but if it works...go with it.

-First off log into your Marriott (Marriott.com) account and uncheck (to not)remember me. You can check your Marriott points and nights totals under overview. Then log out of your Marriott Account.
-Log into your SPG (starwoodhotels.com/preferredguest/about/index.html) is the only site that worked to see my SPG info) account using your email address and password and make sure to uncheck (to not) remember me. If you haven’t logged out of your Marriott.com account and turned off remember me this step of logging into SPG won’t work.
https://www.starwoodhotels.com/prefe...language=en_US
-Drop down below your name in SPG and go to Profile. You’ll see your new SPG number in here.
-change drop down to Overview and you should also see your SPG night totals YTD and Lifetime.
-log out of SPG
-Log back into Marriott.com using your Marriott login and check (turn on) remember me.
-Drop down below your name to Profile.
-here it should display combine your accounts as an option.
-start the process to combine accounts. When it asks to verify your account enter in your SPG account info (I used my email instead of new SPG number assume you could use your new SPG here as well) it’s not wanting your Marriott info here as you’re logged into Marriott with remember you enabled.
-at this stage it will bring up the totals of the two accounts to be merged side by side.
It DID NOT display any lifetime nights totals at this stage only YTD nights for both programs. I almost stopped here but kept going.
-Continue with the combine, it will then pickup your lifetime totals from space and show you the finished product of total nights and points combined.
-At this point I logged out of Marriott.com and then logged back into Marriott to see if it remembered everything and went thru all my account info, overview, Profile, activity. For me, it is all correct.
-After you have combined account and logged back in, you can scroll down in your “overview” to see your Lifetime Status as it shows up below your current status today 1/2 down the second page.
Ie my Status today says Platinum Elite then just below that it says Lifetime Platinum Elite. Then click the arrow beside Lifetime Platinum Elite and it will display your combined lifetime totals including nights and total Elite years at each level.
-The only step left for my account is for it to roll to LTPP on Jan 1st with my 1,100 total combined nights and 17 years as Plat which both displayed correctly in the previous step. Assuming if you had more than 750 spg nights today it would display LTPP now after the combine steps above.

Good luck to all!