Is there such thing as paying a "tax" or "task" on non-spendable bitcoin in a blockchain wallet in order to get the private key? I had bitcoin placed into my account and now am being told it is non spendable and in order to get the private key and make it spendable, we have to pay a fee.
This is a common scam.

If you don't have the private key to begin with, you have no bitcoin whatsoever, and never had any.

Stop talking to whomever is claiming this, and accept your loss.