old dog

no matter what combination of ships i make to form a fleet, I keep geting a notice coming up telling me I must have 2 valid ships, can anyone help, single ships against a fleet is no fun

HI I HAVE JUST HAD THE GAME ONE DAY AND THINK ITS GREAT . BUT,NO MATTER WHAT COMBINATION OF CRAFT I FORM TO TRY AND MAKE A FLEET, I KEEP GETING A MESSAGE THAT I MAST HAVE 2 VALID SHIPS, COULD SOMEONE PLEASE ADVISE ME