This is the first time I've soldered so perhaps something is not soldered correctly.
Yes, that is a workable hypothesis. You should trim the leads short so they don't spill over the edges of the copper and short other things out. It's hard to tell from the photo, but I strongly suspect you have soldering issues.
Try checking the connections with a multimeter (eg. one that beeps for continuity). Check not only that things are connected where they should be, but are not
connected where they should not
be. For example, check that 5V and Gnd are not connected.