GDAT is complicated so when assistance is needed, ask in the Facebook User's Group.
Just asking the question "What did I do wrong?" without details will not get very helpful responses.
Listed here are some guidelines for requesting assistance.
The most frequent and often the hardest to resolve issue is when something goes wrong on trying to load data.
Using a data import template? Identify the data source and verify that the columns in the .csv file match the columns assigned in the data import template. On the F11 page, select the template then paste a line from the file into the test area. Click test and verify that each data item is assigned correctly. If not, you may modify the template to fit your file contents. Note that commas in the data will shew the results. To ask for help:
Identify the data source and detail the steps you took
Post an image of the .csv file contents
Post an image of the data import template being used
Post an image of the Import results page
Post any other images that will help explain the issue