If served with a five day notice to pay or quit is it valid and legal if it has not been signed at all, there is no server signature on it or a notary

A 5 Day Pay or Quit served pursuant to NRS 40.253(1) does not have to be signed by the Landlord or his Agent.  It does not need to be notarized.  However it must be written notice requiring in the alternative the payment of the rent or the surrender of the premises and must (a) identify the court that has jurisdiction over the matter; and (b) advise the tenant of the tenant's right to contest the matter by filing an affidavit with the court that has jurisdiction over the matter stating that the tenant has tendered payment or is not in default in the payment of the rent.