To concatenate cells in Excel, you can either use the concatenation() function or the & symbol. If

A1 = Hello
A2 = World

then

=A1&A2

will produce

HelloWorld

and

=concatenate(A1," ",A2)

will produce

Hello World

If the concatenation is not working, then make sure that the format of A1 and A2 is "text" and the format of the cell with the concatenation function/formula is "general".