Kindly follow the following steps to resolve the issue:
1. Close ERA server and ERA Explorer on your system
2. Go to the drive location of the ERA folder, generally C:\ERA
3. Open C:\ERA\metabase\ro folder
4. Rename Web and download folder to any other name like web_old or download_old
5. Start ERA server again
This will resolve the issue. If the problem continues, then create a SOLAR support ticket.