I will translate for those who do not have English as a first language.
damp squib is a dud.
A squib is an explosive device, when damp it does not go off. You expect a big bang but get nothing.
Thanks for the explanation
it is squib and not squid what I first thought was
Damp Squib or Damp Squid :
Squid are indeed usually damp in their natural environment.
But the popular British expression describing a less than spectacular explosion is a “damp squib” (soggy firecracker).