I figured out what the issue was.
I had already set up an SSL/TLS/HTTPS connection protocol in the opt/tomcat/conf/server.xml file:
<Connector port="8443" protocol="org.apache.coyote.http11.Http11NioProtocol"
maxThreads="150" SSLEnabled="true" >
<UpgradeProtocol className="org.apache.coyote.http2.Http2Protocol" />
<SSLHostConfig>
<Certificate certificateKeyFile="conf/key.key"
certificateFile="conf/cert.crt"
certificateChainFile="conf/chain.crt"
type="RSA" />
</SSLHostConfig>
</Connector>
but the *.war file that was gonna use the connection was not put in the opt/tomcat/webapps directory.
Here's how I solved it:
I simply added the *.war file in the opt/tomcat/webapps directory of tomcat, and then I restarted the tomcat server using:
sudo systemctl restart tomcat
And everything worked fine.
That's all.
I hope this helps