Peugeot 307 2.0hdi 2004 - Dealing with Persistent Error P1435 Despite Multiple Fixes

Hello.
Car and problem as in the subject. So the unfortunate error P1435.
I will write what has already been done. FAP cleaned, fuel additive refilled (level 3/4 of the tank), counters reset, sensor in the fuel cap checked.
Error P1435 means a disruption of CAN communication on the engine controller-additive controller line.
I checked the connections between the add-on controller and the BSI and between the BSI and the engine controller. Everything is OK.
Despite this, the error is permanent and cannot be deleted, therefore the fuel additive is not added.
When I connect directly to the add-on driver, there are no errors, everything plays, the counters clear, etc.
Information about supplementing the additive does not reach the BSI for sure, because after starting the engine it crashes a message about the low level of the additive.
Does anyone have an idea how to get rid of this error because I'm slowly getting helpless?

Oh, the additive pump itself is operational, by entering the additive driver it can be started.
Regards.

Did you reset both counters? the additive counter is also in the engine controller

replace the fap driver

So after three days of fighting I managed to get rid of the error, although I don't know why.

I put the second FAP driver today as advised molasses . Only he had completely different numbers, but that was the only one I had access to.
After connecting and turning on the ignition, a message about too much fluid level (previously it was not enough) and then a second antipollution fault message.
After connecting with the driver, it showed all possible errors. So the driver was from a different version (as evidenced by its numbering).
Basically, I thought nothing would come of it. I plugged the old driver back in and surprisingly it showed the add-on level too high again, not too low as before. Then I deleted the errors and probably for the hundredth time I deleted the counters, including removing the cork. Then I entered the engine controller and deleted the P1435 error.
Imagine my surprise when the error cleared and did not come back. I drove the car from 70 km to test and knocks what everything is fine.
And now I don't know what really happened that the error cleared. Maybe the FAP controller caught some reset after disconnecting, although it's strange because I also tried to disconnect the battery before. I don't know what to think about it.