Is your Cloud Sync enabled on your mobile phone? To check, you can open Rush, locate the project you want to sync and hit the "..." menu to see more options. If your sync is already on, the option will say "Turn sync off." If the sync needs to be enabled so you can see it on your desktop, there will be an option that says "Turn sync on."
If the sync is already on, you can try turning it off, then wait about 5 minutes, then turning it back on, and waiting another 5 minutes before you open it on your desktop. That should give it enough time to re-connect your project to the Cloud.
The other thing to check is to make sure you're signed into the same account on your mobile Rush and your desktop!