Hi,
First thing, did you run through the date-time project and was it successful? If so check below. If not please run through it to successfully build that project as a base line to know how thing should go.
Possible causes could be:
1. Not setting the ant script to refresh after loading:
Solution: Manually refresh using F5 or right click on your project and select refresh.
2. Not setting up the ant script correctly with the start up screen. If you open the config.xml file you should see the name of your start up screen.
Solution: Manually change the config.xml to your startups file. Note: if this is the case your project most likely did not get setup correctly and may not work as expected.
3. If your startup screen is index.html then you could be using an older resource pack that does not overwrite the index.html file.
Solution: manually delete the index.html file and rerun the ant script to update your files.
Thanks,