The code means -- The system cannot find the file specified.
What do you have set up for the task details?
Per the instructs specified in SyncToy Help for scheduling, here is the program action detail:
"C:\\Program Files (86)\SyncToy 2.1\SyncToyCmd.exe -R"
And the trigger detail is:
At 6:30am every Sunday of every week starting 3/9/16

The error suggests that the path to the program may not be properly specified.
Can you execute the task manually from task scheduler?
No, at least not by highlighting the task and clicking on Run

But here is something odd that I don't fully understand. If I go to the SyncToy folder, there are two executable files:
SyncToyCmd.exe (this file doesn't do anything when I click on it)
SyncToy.exe (this file will run SyncToy when I click on it)

But I still can't run SyncToy from Task Scheduler....still get the (0x2) code. I've done more as discussed below in my response to Jay.

-steve

Looks like Steve beat me to the post. I'm still going to leave mine as is but take any advice from Steve before mine.
My response to Steve is shown above

First try running the task manually to see if it works. If not remove the task and set up again.
I can run SyncToy manually from the SyncToy folder, but not from within Task Scheduler. I have not yet removed the task and set it up again (I just now noticed that recommendation...sorry).
Second go to the executable for SyncToy, right click and go to Properties. Under the Compatibility tab select to run as admin.
As I told Steve, when I go to the SyncToy folder, there are two executables:
SyncToyCmd.exe (this file doesn't do anything when I click on it)
SyncToy.exe (this file will run SyncToy when I click on it)
If no success go on to the following.

This is actually an access denied error. The solution you stated is supposed to cure but obviously did not in your case so let's try something else...

Go to http://jaylach.com/downloads and grab the file 'Take Ownership'. Unzip and execute the registry hack to enable Take Ownership in your right click context menu. Right click on all folders that you are syncing and select to Take Ownership. A command prompt will open that automates permission settings, just let it run. Depending on how many files/folders are involved it can take a little time.
I did all the above without any difficulty; and yes, it did take awhile because of all the folders/files I had.
If you go through Event Viewer you MAY find the file/folder that is causing the issue.
I looked at the Event Viewer, but there is just too much stuff there for me to understand.
You can also check the SyncToy logs. You can view the SyncToy log by opening SyncToy, and click on File->View log.
I did look at these logs and there was nothing about a run using Task Scheduler. I did perform a manual SyncToy run earlier this morning, so there were some log notes pertaining to a couple of files they could not read from the Recycle Bin.

Don't quote me on the path as I don't have SyncToy installed. I use GoodSync instead. It is not free but well worth the cost.
https://www.goodsync.com/
I know you and Steve like this program, but the free SyncToy has served me well. It still works fine when I run it manually....I just can no longer get it to execute using Task Scheduler.

Unless you and/or Steve can tell me something else to try, I probably need to remove and reinstall the SyncToy task under Task Scheduler. That's what you meant, right? I shouldn't need to reinstall SyncToy since it works great manually.
You can set the sync to go both directions or just one like a clone. The clone is what I use so my second system data is exactly the same as my main.

I don't see a response...

If you want to try running the executable as admin do both. SyncToy.exe is, as you know, what is used to get the interface on the screen. SyncToyCmd.exe, I believe, is what actually does the sync.

Steve and I did not mean if you could run SyncToy manually but if you could manually run the sync from within SyncToy not using Task Scheduler.

What you did, running the sync, is what was wanted. Just needed to confirm that the sync was still set properly.

Let's see what Steve says. Personally I'm surprised that you got SyncToy to work through Task Scheduler in the first place. I never did although I didn't try real hard.

Specifically, here is my STBatch.bat file:
@echo off
"C:\Program Files (x86)\SyncToy 2.1\SyncToyCmd.exe" -R
pause

And here is my resulting Task Scheduler script:
C:\Users\BB\Documents\STBatch.bat

but I'd exclude (from each other) the files used by both programs to track changes and save copies of deleted files (assuming you have the option set in GoodSync).
Steve, I guess I'm dense, but I have no idea what you are telling me here. Maybe it's because I haven't ever used GoodSync.
-steve

Each program has to keep a sort of data base of what has been done so it is known what is what in relation to the last time ran. If such files are not protected from the other program it can cause problems. Not nearly as drastic but sort of like running two anti-virus programs at the same time.

So how do I know what and where these data base files are? How do I provide this protection?

So how do I know what and where these data base files are? How do I provide this protection?