When configuring Single Logout for an app integration or renewing certificates, the following error might be encountered:
SLO failure: Invalid Signature

• Single Logout
• Single Sign-On
• Error

Invalid Signature means the LogoutRequest is not signed properly. Typical problems would be:

• Signature Hashing Algorithm. .
• Incorrect private key used to sign the message.
• use an external tool to validate the logout request

• Check the Signature Hashing Algorithm (eg: SHA256 or MD5) configured for a partner in IdP.
• The correct public-private key pair is used and associated certificate is configured at IdP and the same certificate is being sent via LogoutRequest.
• Whole LogoutRequest message is signed and not just few elements of the message.

Related References

• Configure Single Logout in app integrations
• Configure Single Logout