In Data Manager, the "Load data" button fetches data from data source for the 1st time. After that, if data source has been modified, clicking "Load data" does not fetch new data.
In Data Manager, what "Load data" button does is "Update the app with changes made in Data manager". It does not rerun the load script. Instead, it fetches data from a data connection called "DataPrepAppCache", which stores data cache of this App and cannot be updated.
In order to refresh data from newly changed data source in Data Manager, a button "Reload table from source" is added to the interface.Note
: After clicking "Reload table from source" and confirm the new data is shown in Data Preview, "Load Data" button is still required to be clicked in order to apply the changes
For more information, refer to Help site: Managing data in apps with Data manager
Instead of using "Load data" button, use "Reload table from source" button. Please refer to the picture: