This is partially our fault as currently Magelo Sync is not compatible with Java 9+ and will probably never be as they have deprecated way too many things.
The plan is to embed the needed JVM with the client so that it is self sufficient and does not need any other parts to run. I will tackle this very soon.
For now, you will have to install the latest Java 8 on your system and the client should be able to find it.
