This error message has been posed on here several times throughout the year and no one ever responds to it or even going back throughout the years all the replies never yielded a fix… **this is especially a big problem if you get this error on a native segwit bc1q address because Counter wallet doesnt show you private keys for it… ** It was kind of a wild trial and error but I never give up and finally got the solution!!!
The Error, Problem & Message:
If you receive the following error you can not send BTC, your “money” or sats are STUCK and waiting will do nothing as time is not a factor. The message reads:
UNKNOWN/Default: JSON-RPC Error:
Type: Server error
Code: -32000
Message: Bad status code returned: ‘500’. result body: '{“result”:null,“error”:{“code”:-26,“message”:“non-mandatory-script-verify-flag (Signature must be zero for failed CHECK(MULTI)SIG operation)”},“id”:0} '.
SOLUTION
In short the fix is you need to restore / Import your wallet into a different non counter wallet but the MAJOR issue is that your 12 word seed phrase is not supported & DOES NOT WORK for imports on most wallets… you basically need to import the private key and that’s you’re only option… but WAIT if you receive this message on a native segwit bc1q address 1. you are not shown a private key so … yeah 2. many people suggest using My Free Wallet because it’s compatible with Counter Wallet… but they don’t use segwit addresses only legacy 1 addresses lol.
So if it’s a segwit bc1q you can’t import seed phrases anywhere and you also have no option to show your private key you basically just gotta go on a trial and error hunt with wallets that show you a native segwit address when importing a legacy 1 like a unisat.io but just wait it get’s more annoying…
I imported my original preloaded first legacy address (start’s with a 1) private key into a unisat.io wallet to see if my segwit addy giving me the problems would be there / match…Sadly it was not there and a different address. This is basically the annoying part, but it will work… you need to generate a new legacy address, look up the private key for that new addy and import the private key onto the unisat wallet and hope your bc1q address giving you the problems reveals itself and is attached to this new legacy address. IF it doesnt… You need to keep doing this over and over until it does. *For me it was on the 3rd created legacy wallet address / 3rd private key import that my segwit addy with the errors finally revealed itself.The good news is CP won’t let you create more than 20 legacy 1 addresses per wallet so the MAX attempts you will ever have is 20.
Once you finally have the right legacy 1 address with the matching native segwit address imported into a wallet like unisat.io just switch to the segwet address and you can send your bitcoin out it and won’t receive the error.
You’re Welcome 