The most reliable method to fix the code 30015 error in Fortnite is explained step-by-step below.
Step 1: You will need to go to the Start menu, search and click on System Configuration.

Step 2: After that, click on the Boot section.

Step 3: Click on the Advanced options…

Step 4: Here, you need to uncheck the Debug and Debug port checkboxes. And then click on Ok.

Step 5: After that, you have to click on Apply, and then Ok.

Step 6: A small window of System Configuration will appear, and you need to click on the Restart option.

Now you are done resolving the issue, and you can launch Fortnite.