It works for me trying to create an output of 2x2 from a single pixel:
x = torch.randn(1, 1, 1, 1)
conv_trans = nn.ConvTranspose2d(1, 1, kernel_size=2)
out = conv_trans(x)
print(out.shape)
> torch.Size([1, 1, 2, 2])

so I guess your setup might be different?