Misplaced space and misplaced apostrophe and missing apostrophe and quote.
This
=DLookUp("[Follow Up Required]","xServices","[Machine No]=' " & [MachineNo] & " AND '[Service Date] =#" & DMax("[Service Date]","xServices","[Machine No]='" & [MachineNo] & ") & "#")
should be
=DLookUp("[Follow Up Required]","xServices","[Machine No]='" & [MachineNo] & "' AND [Service Date] =#" & DMax("[Service Date]","xServices","[Machine No]='" & [MachineNo] & "'") & "#")
Make sure parens, brackets, apostrophes, quotes are always in pairs.