Hey @jjob32, have you gotten this to work yet. If not, here are some tips that you can use to debug. I had this same issues and this is what helped me.
The main thing is to make sure you're generating the constraint string correctly. Because sometimes the constraint is will be causing the query to return an empty list.
To test for this, display your constraint string in your dropsource page and check to see if is correct according to what bubble expects. The constraint string is in the string page variable you created if you were following dropsource tutorial (not the bubble constraint variable).
Next you may want to test your api call with the constraint outside dropsource. I use postman for my tests. If you're making a post/get call to bubble to access your data, you need to be authenticated. There are two ways to do this if you're testing in postman. The first is you can display the access token you saved in your dropsource and copy it so that you can use it in the Authentication header (Bearer ACCESS_TOKEN) in say postman. Alternatively you can first do a post call to your login endpoint in postman and that will return the access token and then you can copy and use the access token for subsequent calls.
The tips above are some of the things i did to debug my app when i faced a similar issue. Through postman i was able to determine the right column name and constraint function to use. For example i realized that for some columns using "text contains" didnt work and i had to use "equal" and vice versa.
Hope this helps.