if deactivate both, do I need to activate them manually or I start the movie studio 15.0, it will automatic activate the two computers?

Go to your Magix Account

Search your software

And deactivate both.

Now you can for each computer activate them again.

on the software 15, I can only see "deactivate the sofware on this pc...", but I can not find a way like "activate software on this pc..."

I already deactivate both my computers, I tried to re-activate both computers, but I can't, it ask me computer ID, which I entered, still not working.

it keep show a note as pic attached, I still can not find a way to reactivate my computer, search on help, nothing there show how to reactivate or deactivate machines. so hard to work with it

The general advice (which applies to MSP as well) is in the FAQ p.9:

"You can use VEGAS Pro (14.0 and later) simultaneously on 2 devices. There are 2 ways to deactivate a device so you can activate a different one:

Visit your MAGIX account > My Products > Show More Details > Deactivate. This option can be used only once a month.

From the VEGAS Pro Help menu choose Deactivate the Software on this PC. This option can be used as often as you wish. An internet connection is required."

You may need to contact Support with your problem.

here is a pic show both computer had been deactivated

so the movie studio 15 can not switch my pcs as often I need? every month can only do one time?

I am upgrading win 10 for my pcs from win7, most my Dell laptops have problems after upgraded to win10, such as SD card can't read, CD /DVD drive missing is OS, I try to install the movie studio on a few pcs to see which one works better.

"From the VEGAS Pro Help menu choose Deactivate the Software on this PC. This option can be used as often as you wish. An internet connection is required."

the one i have is not Vegas Pro, it is Movie Studio Platinum 15.0

if i uninstall Movie Studio Platinum 15.0 on my pc, reinstall on another pc, will this way work?