If you recently bought crypto, your purchase may be subject to a 7-day holding period. During this time, you will still be able to use your recently purchased funds to fund additional buy orders, sell orders, and Swap trades (coming soon); however, these funds will not be available to withdraw or send to your non-custodial wallet.
then blockchain.com shortened it to 3 days which is now what we are seeing in the live article.
@op, did you buy using your card? then reach out to their support if three days has passed and the problem still persist. I'd escalate it thru their twitter too (https://twitter.com/AskBlockchain)