Check that your staked SOL completed the delegation or undelegation process, which takes 2 epochs. Epoch 1 will be utilized to lock your SOL, your rewards will be generated starting on epoch 2. This works the same when unstaking. You will receive your last reward on epoch n+1 and your SOL will be unlocked at the end of epoch n+2. You can check how long the current epoch will take to complete on the a Solana blockchain explorer.
2. If you don't have enough SOL balance to pay for transaction fees, you won’t be able to undelegate any staked SOL. Remember fees will vary from validator to validator, and your SOL balance on your main account will be the one where the fees will be deducted from, not your staking account. As a rule of thumb, we recommend always keeping 0.1 SOL in your wallet to avoid worrying about having enough SOL to cover fees.
3. The staked SOL won’t automatically go back to your main account once the undelegation is completed, you must either withdraw a certain amount, or close the account, which will send all of the remaining SOL on it to your main account.
If you’re still having trouble unstaking on a legacy Keystore Solflare wallet, we recommend getting in touch with support.