If you are using a SHA-1 signed certificate for your RA webserver depends on how you configured your Release Automation server.
When you are using the secure communication (HTTPS) between internet browser and RA server and use the default nolio self-signed certificates
installed during the installation, you have a SHA-1 signed certificate in place which needs to be updated.
If you have already setup you own certificate from a Certificate authority or generated your own self signed certificate you have to verify the certificate.
In most browsers you can click on the padlock symbol to display the certificate information. Expand to show certificate details and check the Signature Algorithm. Also make sure you click on the intermediate certificate to check if this is SHA-1 signed certificate or not.
As a best practice we always advice to replace the default nolio certificate for your own certificate.
You can install your own self signed certificate using the procedure "Secure UI Communication” from the Release automation installation guide