Flow fcl verifyUserSignatures Error

I am trying to authenticate the owner of the account in the backend so I am using account_proof. Before I tried using 'accessNode.api': 'access.mainnet.nodes.onflow.org:9000' but it gave me this error

Error: Response closed without headers

so I found a workaround which was to use 'accessNode.api': 'https://access-mainnet-beta.onflow.org' and it was working fine yesterday but now it is giving this error

Error: failed to execute the script on the execution node execution-0[email protected]execution-004.mainnet16.nodes.onflow.org:3569=100: rpc error: code = InvalidArgument desc = failed to execute script: failed to execute script at block (10cdbef077586db57b2949cd02e34cd0c051c2b236be1d828ecc2d227b93b73f): [Error Code: 1101] cadence runtime error Execution failed:
error: invalid argument at index 0: decodeing argument failed: [Error Code: 1052] transaction arguments are invalid: (argument is not json decodable: failed to decode value: invalid JSON Cadence structure)
--> a781c6cb2e8dc91d9e2e4a60358d60b61ea9f7215acae192a32cfeaffe7028e9

How can I solve this?

BTW I am using this method to verify the account Proving Ownership of a Flow Account - Flow Documentation

You can check for this.

"accessNode.api", "https://flow-access-mainnet.portto.io"

Hey thank you for the comment I used your solution and found a very weird error

 ` let data = blocto.services[5]?.data;
    const address = data?.address;
    const timestamp = data?.timestamp;
    const Message =await WalletUtils.encodeMessageForProvableAuthnVerifying(
      address, // Address of the user authenticating
      timestamp, // Timestamp associated with the authentication
    const CompositeSignatures = await fcl.currentUser().signUserMessage(Message);
    const isValid = await fcl.verifyUserSignatures(Message, CompositeSignatures);
    const CompositeSignatures2=data.signatures;
    const isValid2 = await fcl.verifyUserSignatures(

What is the difference between isValid and isValid2. isValid works perfectly fine but isValid2 throws an SyntaxError: Unexpected end of JSON input error. Please help I have been trying to solve the issue for hours but getting no where. Also I console logged the compositeSignatures and compositeSignatures2 and these are the results

compositeSignatures: [
addr: "0xca5b85f57d71f86d"
f_type: "CompositeSignature"
f_vsn: "1.0.0"
keyId: 1
signature: "4bf89cc644f13cebc339d2ccc31c554c0511d2bc8dd40ec56aad3126717e79000845f81844fcffea11b5096c91e802918d221e557b37808fc2539896b6b7a38b"
[[Prototype]]: Object
length: 1
[[Prototype]]: Array(0)
{ 0:
addr: "ca5b85f57d71f86d"
f_type: "CompositeSignature"
f_vsn: "1.0.0"
keyId: 1
signature: "218920f58af615f69c9fef668d23a076073e943fdfa987bb63220dcc7fd8435f33dc0ce4853c36ac96a4ab10188db211808479b2461ec44b0d3a1d34ac052eb4"
[[Prototype]]: Object
length: 1
[[Prototype]]: Array(0)}

As for my understanding, at first in flow isValid2 was used but after the upgrade, right me if I am wrong, I think so now isValid2 may be deprecated therefore it is giving a strange error. you can also check this post