Your board looks good for a first try or two. Your problem is like the others said “a short”. Are the stand-offs causing the trouble? Looks close in the picture. An exacto knife or insulator will fix it.

A few more things to keep in mind for the next one.

Traces should be no closer than 0.007 to each other 0.010 is better.

If VSS and VDD are next to each other, try to allow more, 0.010 may not be enough in the long run. Solder will grow “whiskers” over time and cause the gap to close. The more amps the more gap and wider the trace.

Clean all rosin from the board. Rosin will become conductive at elevated temperatures. Then use a sealer when finished testing. Spray lacquer works good to keep the air off.

Think of you board as a capacitor. Components and traces from top to bottom may have a capacitor effect. The large fields of copper that mister e spoke of will add to this problem. For fun you can build high voltage caps from pc board.

Most of all triple check your routing.

You will pick up more as you go.