Slack Test connection fails with PKIX path validation failed #753

Jenkins version is 2.263.1-LTS
Slack Notification Plugin - 2.45
Java Version - openjdk version "1.8.0_275"
OS - CentOS -8.2
Problem: Under Manage Jenkins > slack - Test connection shows failure. In my Jenkins Systems log shown below error message.
Error posting to Slack
java.security.cert.CertPathValidatorException: Algorithm constraints check failed on keysize limits. RSA 1024bit key used with certificate: CN=slack.com, O="Slack Technologies, Inc.", L=San Francisco, ST=California, C=US.  Usage was tls server
	at sun.security.util.DisabledAlgorithmConstraints$KeySizeConstraint.permits(DisabledAlgorithmConstraints.java:819)
	at sun.security.util.DisabledAlgorithmConstraints$Constraints.permits(DisabledAlgorithmConstraints.java:421)
	at sun.security.util.DisabledAlgorithmConstraints.permits(DisabledAlgorithmConstraints.java:167)
	at sun.security.provider.certpath.AlgorithmChecker.check(AlgorithmChecker.java:326)
	at sun.security.provider.certpath.PKIXMasterCertPathValidator.validate(PKIXMasterCertPathValidator.java:125)
Caused: java.security.cert.CertPathValidatorException: Algorithm constraints check failed on keysize limits. RSA 1024bit key used with certificate: CN=slack.com, O="Slack Technologies, Inc.", L=San Francisco, ST=California, C=US.  Usage was tls server
	at sun.security.provider.certpath.PKIXMasterCertPathValidator.validate(PKIXMasterCertPathValidator.java:135)
	at sun.security.provider.certpath.PKIXCertPathValidator.validate(PKIXCertPathValidator.java:233)
	at sun.security.provider.certpath.PKIXCertPathValidator.validate(PKIXCertPathValidator.java:141)
	at sun.security.provider.certpath.PKIXCertPathValidator.engineValidate(PKIXCertPathValidator.java:80)
	at java.security.cert.CertPathValidator.validate(CertPathValidator.java:292)
	at sun.security.validator.PKIXValidator.doValidate(PKIXValidator.java:381)
Caused: sun.security.validator.ValidatorException: PKIX path validation failed
	at sun.security.validator.PKIXValidator.doValidate(PKIXValidator.java:386)
	at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:291)
	at sun.security.validator.Validator.validate(Validator.java:271)
	at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:315)
	at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:223)
	at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:129)
	at sun.security.ssl.CertificateMessage$T12CertificateConsumer.checkServerCerts(CertificateMessage.java:638)
I have no issue in installing and updating the Jenkins plugins.
Have followed the instructions provided in this link - https://support.cloudbees.com/hc/en-us/articles/217078498-PKIX-path-building-failed-error-message
However i have no success. So please help me to resolve this issue.