Thanks so much. sometimes when I use collect it gives me 5 rows where is written
[ canonicalCoordinates, ChangeSymmetry, CharacteristicQ, D_Dx, DeterminingPDE, `Ηk`, FromJet, InfinitesimalGenerator, Infinitesimals, InvariantSolutions, InvariantTransformation, Invariants, PDEplot, ReducedForm, SimilaritySolutions, SimilarityTransformation, SymmetryTest, SymmetryTransformation, TWSolutions, ToJet, build, casesplit, charstrip, dchange, dcoeffs, declare, diff_table, difforder, dpolyform, dsubs, mapde, separability, splitstrip, splitsys, undeclare ]
and the only way that I found to go ahead is to recompile with !!! and so it works! do you now why?