Scenic wont start after dephaser changed

Hello, can anyone shed any light please

Partner has just changed the dephaser pulley on my 55 plate scenic, also changed spark plugs.

But now it wont fire up at all?

Is there anything needed to be done that cant be done at home after dephaser is changed or anything?

Well and truly stuck!

Thankyou

Scenic wont start after dephaser changed