Originally Posted by Ptech1

You need to remove and check your charcoal canister by blowing air directly through it from the lower hose connection (tank side) . I've personally seen several cars where the initial chamber (there are 4) basically molds while turning the desiccant material solid. This causes a restriction and doesn't allow the tank pressure to travel through the canister to the purge valve while fueling.
If you don't get air flow while checking it, then you'll need to either purchase a used unit (no longer available from Porsche), or cut the charcoal canister open at the seam and hollow out/remove the material from that initial chamber, and then reseal it with epoxy etc as any leak will cause a CEL. Unsure if you can break it apart through the inlet/ tank connection as I haven't personally tried it, but was part of a discussion with my techs.
I​​​​'ll see if I can find the photos I took of the first one we found after going through the entire system to resolve a consistent fueling issue.
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Originally Posted by Edcantera

Sounds like a plugged up canister not letting the vapors in the tank enter the canister. I’d investigate the canister.