MATCH or VLOOKUP can not find matching cells

I've got a worksheet ('1') that has a column of dates ("dd/mm/yyyy hh:mm") which is not linked from anything (it's just a list) and another column with 'values' corresponding to those date/time stamps.
A second worksheet ('2') has date/time and 'values' pulled in from an outside source (OSISOFT PI). I want a third worksheet to match the date time 'values' for the first worksheet
In this third worksheet ('3') I have the date/time range in column A taken from the second worksheet because it is a dynamic date/time range. the 'values' are for argument sake in column 'B'.
The problem is that it matches (or finds) some of the values but not all. For example:

.
.
01/01/2015 00:10 313.7
01/02/2015 00:20 315.7
01/02/2015 00:30 #N/A
01/02/2015 00:40 314.9
01/02/2015 00:50 313.7
01/02/2015 01:00 #N/A
.
.
I've gone through and tried to find "phantom characters", but can't see anything . What confuses me is that it seems to work for some values and not others.

Can anyone help with this?

If you only display hours and minutes, there might also be seconds in there which you are not away of, and if you are trying to do an exact match then you won't find one. How are you bringing the data from sheet2 to sheet3 (i.e. what formula are you using)? You might be able to include a CEILING function or TRUNC function in there to ensure that you do not have any seconds - hard to say exactly, without seeing your workbook.

Hope this helps.

Pete

Right, I've changed the workbook around a bit so it's manageable but still contains the same problem.

When I change the date/time format to number format, they are the same even to 15 decimal places. Still confused.

Book2.xlsx

Any help would be huge!

Thanks!