The panel might be experiencing a deep discharge. Here's a step-by-step guide to address this issue:
Disconnect both the battery and the AC power.
Reconnect the battery only.
Plug in the AC power, wait for 5 seconds, then unplug it. Repeat this process up to 10 times until the LEDs flash red continuously, indicating that the battery is charging.
Allow the charging process to continue for up to 30 minutes. The panel should automatically boot up once it has sufficient charge.
Please note: If the LEDs stop flashing red and the panel doesn't boot up, repeat the process starting from step 3.