Do you have mature coins? If you were sending them from one address to another you must wait 1h and restart the wallet.
Open your wallet, click on the icon with working-instruments (wrench&screwdriver), click Console tab, and input

getstakingstatus

You should get smth like this:



{
  "validtime": true,
  "haveconnections": true,
  "walletunlocked": true, ===========if you LOCKED your wallet with a password, staking won't work!
  "mintablecoins": true, ==============if you have mature coins it is TRUE
  "enoughcoins": true,
  "mnsync": true, =============if the wallet is fully synced
  "staking status": true ============if staking=1
}