A few tips that will help you troubleshoot moving forward:
- Use the issue tracker. This will usually tell you valuable information about what the problem is. You always want to have no issues here. If you have any, you should work on removing them.

- In your case, the issue will say something like this (except yours will say customers where mine says teams):

The issue is telling you that Bubble is looking for a single customer while you are trying to send a list (many).
To fix this:
- Leave the data to send blank. This should be used when the destination page is for a single record. Since you are going to set up a list on the destination page, you don’t need to fill it in.
- Retrieve the list of records once you are on the customer page. You will do this within the repeating group you set up by doing a search in the data source.