I assume your STX is still on Blockchain.info then you can get the 12 word backup pharse on the "security" option and import it into official Stacks Wallet [1]
I don't know if it's will solve the problem or not, because the STX coin has a "transfer lock and time lock" [2] But, it worth to try... If you still can't transfer after you using Stacks Wallet, then the problem is about the coin not the exchanges/third parties.
[1] https://www.hiro.so/wallet/install-desktop
[2] https://blockstack.zendesk.com/hc/en-us/articles/360043012494-What-types-of-transfer-or-time-locks-are-Stacks-tokens-subject-to-
I don't know if it's will solve the problem or not, because the STX coin has a "transfer lock and time lock" [2] But, it worth to try... If you still can't transfer after you using Stacks Wallet, then the problem is about the coin not the exchanges/third parties.
[1] https://www.hiro.so/wallet/install-desktop
[2] https://blockstack.zendesk.com/hc/en-us/articles/360043012494-What-types-of-transfer-or-time-locks-are-Stacks-tokens-subject-to-
A year larter and still nothing form Blockchain!