How can I see why products are not being synced
In your product list “All Products” you will find a column called PayPal Zettle Status which displays information about the product sync for each product.
This column can be disabled via the Screen Options.
When your products are not synced, you should find more information about what happened in the PayPal Zettle log files.
You can find the PayPal Zettle log files here:
WooCommerce -> Status -> Logs -> select “zettle-pos-integration[…]” in the dropdown menu on the right side