depollution system fault?

my car peugeot 207,afther replace 2unitssolenoid valve,1unit up stream oxygen probe,1unit downstream oxygen probe,1unit switch kit as per instruct technical peugeot jakarta .
afther replace all switch sensor ,technical start engine lamp depollution system at dasboard clear but afther cut off engine n key take out n afther n start engine again,lamp at dasborad give warning again depollotion system fault .
ps adv what kind mistake instal by technical.any body can help me gv info for soulutin