First of all, you should make sure that you have updated to the latest version of the game through Google Play or the App Store. Also, check what Google / Facebook account you have logged in, and if this is the one you have first connected with Idle Space. Always use the same account that you connected with in the beginning!
Then, check if your device date & time is set correctly and you have a stable internet connection. Even though Idle Space is playable offline, some in-game features do require that your progress is properly synced with the server before accessing them in order to prevent errors.
Furthermore, sync errors may appear when playing simultaneously on multiple devices with the same user, which is intended behavior to prevent fraud.
If this didn't help, feel free to contact our customer support via e-mail: firstname.lastname@example.org