To sync products, you need to have a maintenance plan. Upgrade maintenance plan to ensure all SKUs get synced.
You simply need to add the number of SKUs you want to sync on the plans page and upgrade the plan once. For more details, please check the below image.
Once done, you can perform Sync all operations or wait for the Connectr app to auto-sync the product in the next 24 hours as per the settings set in the Connectr dashboard.
For your reference - How the app works? and Sync Feature