I've found that launching replication monitor feature from SQL Server Management Studio connected to Azure Manage Instance public endpoint doesn't show data.
I worked on a service request that we found that using SQL Server Management Studio connected to the Azure Managed Instance Public Endpoint doesn't show data, however, using the private endpoint we have all the details.
Why?. Running SQL Server Profiler Trace I've found that Replication Monitor executes the following TSQL: exec sp_helpdistpublisher N'servername.PUBLIC.clustername.database.windows.net,3342' that tries to retrieve information about the replication definition details, but, the information is saved using the private name. So, using the Azure Managed Instance Private endpoint like this one: exec sp_helpdistpublisher N'servername.clustername.database.windows.net' all information is obtained.