Your product data source contains an invalid character for the current encoding setting. To change a file's encoding settings in your Google Merchant Center:
1. In your Merchant Center account, select Settings in the left navigation menu.
2. Select Data sources.
3. Under the 'Product sources' tab, select a product source.
4. On the page that loads, select the Data source setup tab and select the arrow to expand 'Show advanced settings' if it isn't already expanded. Then, select the pencil icon next to the 'Encoding' option.
5. Select the correct encoding option.
6. Select Save.
Note: You'll have to resubmit your product data source for this change to take effect.