As already indicated (above) using Grub to boot Grub in a multi-boot scenario has the potential for all kinds of annoyance.
Instead, try using rEFInd as your initial boot manager, to effectively chainload the Windows bootloader, any Grub instances present (Manjaro, and whatever other Linux you have in the mix).
I mention it toward the end of this tutorial:
Using refind is a convenient method to boot each OS on your system, and there are also other advantages which you will discover along the way.
Regards.
Welcome to the Manjaro community
As a new or infrequent forum user, please take some time to familiarise yourself with Forum requirements, and the many ways to use the forum to your benefit.
To that end, links are provided (below) - Please use them.
Be prepared to provide outputs from various commands when asked. It’s equally important to provide as much actionable information as possible in your first post, rather than simply indicating there is a problem.
Waiting for others to blindly ask questions can be counter-productive – typically, nobody has a 
at their disposal – Instead, please help others to make informed suggestions, based on information you provide.
Update Announcements
The Update Announcements contain important information and a Known Issues and Solutions section that should generally be checked before posting a request for support.
System Information
While information from *-fetch type apps might be fine for someone wishing to buy your computer, for Support purposes it’s better to ask your system directly; 
Output of the inxi command (with appropriate parameters, and formatted according to forum guidelines) will generate information useful for those wishing to help:
inxi --filter --verbosity=8
or the short form (preferred):
inxi -zv8
- inxi man pages (Arch Manual)