Why does a SyncMe shortcut run only "once"?
Android gives activities a setting called launchMode, which allows them to control how and when they're launched. With some values of launchMode, starting the same activity again with an intent won't start a new activity: instead, it'll deliver the new intent to the existing activity. This might happen only if the activity is the foreground activity, or if it is anywhere in the current task (that is, if you can get to that activity just by pressing back repeatedly).

It's quite common for app authors to set launchMode to solve some kinds of programming or user interface problem, such as concurrency issues that arise from having two instances of the same activity running at once, one in the foreground and one in the background. When they do this, they don't always remember to write the code to handle the new intent the activity is sent by Android: the activity receives the intent a different way to when it's first launched.

It's hard to tell without knowing more about this app, but from the behaviour you describe, it sounds like SyncMe has fallen into this trap. You should tell the developer what you're trying to achieve, and ask them to fix it.