Why does the DL400 Pro Screen Tester show "Unknown FPC"? Solutions!
The DL400 Pro screen tester supports iPhone 6-17 Pro Max, Samsung, Huawei, and more. But when you see "Unknown FPC," it means the tester cannot recognize the connected screen.
Here are five potential solutions that might work.
1. Check connections. Ensure test FPC flex cable, phone screens and DL400 PRO tester are firmly connected.
2. Update software. Newer models (like iPhone 17 series) require the latest software.
3. Use the latest DL400 Pro socket, now it's V4.0 socket.
4. Use the EDP Board. Required for iPhone 13 Pro–17 Pro series models
5. Use new test FPC flex cables. Old FPC cables are incompatible with new software.
6. Make sure your DL400 PRO is 32GB.
You can search "DL400 PRO" on the DIYFIXTOOL website to find the latest software and all compatible accessories.
Posted Jun 27, 2026, 7:19 AM UTC