Also, be sure that the contents are on the drive correctly. Like I said, you can't just copy the single .iso file to the jump drive.
Make sure you did this correctly:
USING THE WINDOWS 7 USB/DVD DOWNLOAD TOOL
Before you run the Windows 7 USB/DVD Download Tool, make sure you have already purchased the Windows 7 ISO download from Microsoft Store and have downloaded the Windows 7 ISO file to your hard drive. If you have purchased Windows 7 but have not yet downloaded the ISO file, you can download the file from your Microsoft Store Account.
TO MAKE A COPY OF YOUR WINDOWS 7 ISO FILE:
Click the Windows START button, and click WINDOWS 7 USB/DVD DOWNLOAD TOOL in the ALL PROGRAMS list to open the Windows 7 USB/DVD Download Tool.
In the SOURCE FILE box, type the name and path of your Windows 7 ISO file, or click BROWSE and select the file from the OPEN dialog box. Click NEXT.
Select USB DEVICE to create a copy on a USB flash drive or select DVD disk to create a copy on a DVD disk.
If you are copying the file to a USB flash drive, select your USB device in the drop-down list and click BEGIN COPYING.
Then when those files are on the jump drive exactly the way it instructs above, run the MakeBootable app on it.