Re-download the firmware. It may be corrupted or not intended for your specific screen resolution.
If you used a custom launcher or third-party apps, you may need to re-configure them. Troubleshooting Common TS907 Firmware Issues ts907 firmware
For the most stable, community-tested versions of TS907 firmware, search for "HCTGO firmware," "MT8227L firmware," or check the 4PDA forums, which are known for hosting many modded and stock updates for Chinese Android head units. Re-download the firmware