I am fixing a 2 nd hand Severne Dyno V2 (2020) , this board had water because a defect Goretex air breather plug.
I ordered at my local surf shop a new Severne Goretex breather, but I have troubles instaling the plug because the thread M12x,1.5 from the new breather plug don't fit propper in the board. Is it possible that my board has a diffrent screw thread in the breather plug?

maybe consider installing a standard breather instead while you are repairing the board. Many are not a fan of gortex breathers, they are set and forget but a pain when they fail

Agreed with the above
And they dont bresthe if the core is still wet

As far as i know they are all the same, i have nixe all different brands and never found a different thread
Severne do it properly - a thin wipe of silicone on threads before installation - so have you confused messy silicone for damaged threads?