Why my coins not stake? they are all spendable
They try to stake... Each wallet talks to everyone else, and they have a difficulty number to beat. This difficulty number helps keeps the blocks 60 seconds apart, as it will average out to. The wallets get this by some calculation on the age of the coins and the size of the piece, the bigger and older, the better chance you have. If you turn on coin control, then choose to send, and choose the input, you can see your pieces.
Take, for example, the coins I think will stake next for me. 1432 coins in one spendable output that has aged 15137 confirms so far, that's about 252 hours old. If you look at one of the recent blocks created, block 47054, it was about 24563 Kobo and it was generated by the creation of block 44877. It had 2176 confirmations when it split--about 36 hours after generation. I chose that block since it was a super easy one for an example, that was the second time that address staked.
So lets say those coins, that created block 47054, had a rating of 53,449,088 (age times size). My next stake would rate as 21,676,184 now--looks like it still has a ways to go. This is just a basic example of how it works. Depending on the time of day and who has their wallet open, means some times it's easy for lower difficulties, other times it's hard.
