question

Again, you're just behind the curve. You've used more battery capacity than you can replace with solar in a single day, and it's likely been cumulative over time. Since you don't have a battery monitor, you have no idea what your state of charge is. Here's a set of charge and discharge curves:

I have added red lines for 3.3V and 3.4V/cell levels (13.2V and 13.6V, respectively)

The solid red line is a 0.05C charge current. In your MPPT cap above, you are charging at 5.6A. This is 5.6/400 = 0.014C, so you're not even charging at this rate - meaning your charge voltage will be even lower than the chart indicates.

It's very important to realize that only a 0.4V change in battery voltage covers 60% of the battery capacity... LFP voltage is very consistent even with large changes in charge.

To say it other ways:

If you're charging at 20A, then you will indicate 13.6V or lower until you hit 95% charge.

If you're charging at 40A, then you will indicate 13.6V or lower until you hit 80% charge.

If you're charging at 20A, then you will indicate 13.2V or lower until you hit 20% charge.

If you're charging at 40A, then you will indicate 13.2V or lower until you hit 17% charge.

Given that you're showing < 13.12V and charging at an even lower current, your battery is at an extremely low state of charge.

You likely need at least 2-4 days of excellent solar conditions (no shading from sunrise to sunset with array at optimal orientation) with ZERO loads of any kind before you can fully charge your battery.

Look at the Wh your array is producing. If you use more than that on a daily basis, you will eat away at your battery state of charge.

On days 20 and 21, you generated a total of about 1100Wh or 550Wh/day average. Looking at days 9-13, you are producing more than this on average, yet you are unable to attain peak voltages. This indicates you are using more than you are taking in.

Recommend you get a smartshunt, so you know your actual state of charge for the future.