If you have access to your current account but wish to sync your progress on a different device or Steam client, you must do the following:
Enter your (old) device with your current progress, and enter the Settings Menu( Gearwheel icon in the top right) > Restore account.
Follow the instruction written there, as described here:
After this, you should be able to play on your desired account.
If you cannot access your old device or current account, please read the "Account Restore and Transfer" article in the "Account and Payment" section to contact Customer Support regarding this.