I imported a bitcoin address to my block-chain wallet. The bitcoin shows as un-spendable in the wallet. The address was used previously by me and worked fine. How do i fix the problem to make the spendable.
Assuming this is a standard P2PKH/P2WPKH address, your wallet will need knowledge of the private key that was used to derive this address, in order to spend the funds locked to it.
Addresses are public info, so when you 'import an address' to a wallet, that just means you have instructed the wallet to watch that address, and report back the apparent balance of it. Anyone can do this with any address, since they are public knowledge.
In order to spend those funds, you would need to 'import a private key' to your wallet (and then ensure that your wallet derives the correct address from that key, eg, segwit vs legacy addresses). Your wallet will then be able to use this private key to create a signature on a transaction that spends those funds.