The update UI was removed from the UI in 6.0 so customers must use the CLI. The current example in the 6.0 docs for running update will not work when update from 6.0 to 188.8.131.52. See https://backstage.forgerock.com/docs/idm/6/install-guide/#update-cli
For 5.5 to 6.0 you have this:
However, for 6.0 to 184.108.40.206 customers will need to add the --skipRepoUpdatePreview flag since this is a patch release (case may be different if this was a maintenance release such as 220.127.116.11).