FTW +1
Now that is funny.
OP...new wheelset has smallest rear cog likely slightly outboard of old wheelset cassette smallest cog. You will also need to adjust your cable tension.
If your cable isn't sticking and your rear derailleur spring is still strong, it comes down to the small cog limit screw and/or cable tension.
To get the derailleur to shift more outboard you need to loosen the limit screw and/or loosen the cable.
Nothing to it really.