Was mailed a cashier check from 3rd party for my refund amount and no one will cash it

Deposit the check into a bank account.  Wait for the deposit to clear and then you can withdraw the funds.

TurboTax cannot help with that.   We do hear that sometimes such checks can be cashed at Walmart.   If you are not able to do that, it is a good idea to open a bank account at an actual brick and mortar bank---then you can deposit the check, wait for it to clear and spend it as needed;   if you have a bank account then you have somewhere to go and interact with humans face to face if you have issues such as this.