The public keys generated by generate-stacking-signature and check-config don't match. I've used the public key generated by stacking signature command in stack-aggregation-commit contract calls and the signer is not registered for cycle 84. The private/public keys are generated directly off secp256k1 package in node:

const EC = require("elliptic").ec;
const secp256k1 = new EC("secp256k1");
const enc = require("@stacks/encryption");
const process = require("process");
const key = secp256k1.genKeyPair();

while (true) {
  const key_hex = key.getPrivate().toString("hex");
  if (key_hex.length != 64) {
    continue;
  }
  break;
}
try {
  const privateKey = key.getPrivate().toString("hex");
  const publicKey = enc.getPublicKeyFromPrivate(privateKey);
  process.stdout.write([publicKey, ":", privateKey].join(""));
} catch {
  return process.exit(1);
}
return process.exit(0);

generate-stacking-signature response:

$ ./stacks-signer generate-stacking-signature --pox-address <> --reward-cycle 84 --config ./signer.toml --method agg-commit --period 1 --max-amount 500000000000 --auth-id 0

Signer Public Key: 0x0303144ba518fe7a0fb56a8a7d488f950307a4330f146e1e1458fc63fb33defe96
Signer Key Signature: <>

check-config response:

$ ./stacks-signer check-config --config signer.toml 
Config: 
Stacks node host: 127.0.0.1:30443
Signer endpoint: 0.0.0.0:30000
Stacks address: SPYQ2Q584Y5059SEVN695YREBZ3RPJ68GJBQTPV8
Public key: 0403144ba518fe7a0fb56a8a7d488f950307a4330f146e1e1458fc63fb33defe96193e4d30f75dc540cc29c27de85a0233bd084628d430add9c2229cdebe55a997
Network: mainnet
Database path: /stacks-blockchain/signer/signer.sqlite
DKG transaction fee: 0.01 uSTX

Using stx get_address <privKey>, @stacks/transactions package and check-config all point to the address SPYQ2Q584Y5059SEVN695YREBZ3RPJ68GJBQTPV8, while the public key generated from generate-stacking-signature matches the address SP2H1N2V9S7PEBC0120S3WMEAT32B9N7CGMPSGF16 (checked by @hstove).

On another note, the public key generated by generate-stacking-signature is the same one that is being generated in the node script (process.stdout.write([publicKey, ":", privateKey].join(""));).

I haven't seen other signers run into this issue, so that makes me think if it's because of the way the private key is being generated.