Add blue is pig pi** and its used in add blue systems in trucks.

You need an eloys fluid from Peugoet , they will tell you which one for your vehicle. Its a lot more expensive than Add blue !

The cars ECU needs to be reset after the tank is refilled but often the tank needs cleaning first before refilling as the sensors give problems.

You will need to find a good indy with the correct diag kit and the knowledge to add and reset if thats what the problem is ! quite often its just the magnet fallen out the fuel filler cap

I sugest you get a diagnostic check to trace the scource of the fault, it could be anything from the fuel filler cap to blocked exhaust. Have you tried giving it an italian tune up ? or it it on reduced power ? Its possible that its just running a fraction more smokey and the Cat is more blocked than usuall triggering of the APF. Try a good blast first and then a fault code read