Quote from: recode6 on Today at 11:27:27 AM

I still have a private key from an old Bitcoin wallet (circa 2012), and I have a private key.

That's probably a valuable wallet, so you should NOT enter the private key into a hot wallet, risking everything if your wallet gets compromised.

Quote

I downloaded the bitWallet app for iOS, entered my private key there and my wallet with balance and all transactions was displayed. I wanted to transfer bitcoins to my new wallet, but I get the error mandatory-script-verify-flag-failed (Public key is neither compressed or uncompressed)

I don't use iOS or bitWallet, but I can recommend Electrum. Even better if you do it securely, by keeping the private key offline. This is how I would do it:

Quote from: LoyceV on February 19, 2021, 05:35:55 PM

Online:
Install Electrum on your PC.
Import your address to create a watch-only wallet.
Preview the transaction, Copy the unsigned transaction. Put it on a USB stick.

Offline and running without hard drive storage:
Get a Linux LIVE DVD. Use Knoppix or Tails for instance, or any other distribution that comes with Electrum pre-installed.
Unplug your internet cable. Close the curtains. Reboot your computer and start up from that DVD. Don't enter any wireless connection password. Keep it offline.
Start Electrum. Import your private key.
Copy your unsigned transaction from the USB stick, load it into Electrum.
CHECK the transaction in Electrum. Check the fees, check the amount, check all destination addresses (character by character).
If all is okay, sign the transaction. Copy it back to your USB stick.
Turn off the computer. That wipes the Live LINUX from memory and all traces are gone.

Online:
Use your normal online Electrum to (check again and) broadcast the transaction.

Bonus:
After moving all your Bitcoin, and once the transaction confirmed, check if you own Forkcoins.