Here is a question I recently recived regarding Shopify and Google Ads/Google Shopping:
When Google Ads says something like Limited By Daily Budget but is not spending the whole budget that usually tells me that it is still optimising. If this is the case give it time and let it finish optising.
Google Shopping can take 5-14 days to fully optimise when you make any changes.
Hope that helps, if you have any questions please ask them below.
Thanks for reading cheers!