B1DI test connection error: HTTPS roundtrip

Hi all,

I have setup a SLD to SBO 8.8 and the JDBC connections works fine, but trying to test de B1DI connection the system returns the error

"XCE001 Nested exception: java.rmi.RemoteException: Error on completion of HTTPS-roundtrip: java.net.ConnectException: Connection refused: connect; nested exception is: java.net.ConnectException: Connection refused: connect"

I have already checked:

-IP of the DIProxy host

-Firewall

-diproxyserver.properties file

What could be the problem and its solution? Version of Integration Framework is 1.22.0

Thanks in advance.