Audi Rs6 C8 Particulate Filter

[Ultimatenemesis]

Having a problem with my c8 audi rs6 2020

The particulate filter warning came up a few days ago and since then the cars start/stop doesn't work and ot has become really sluggish.

I did take it for a drive at 70mph with high revs for about 30mins and the warning disappeared but the car is still very sluggish and the start stop still doesn't work.

Any idea what's the issue?