When onboarding your SQL Server instance to Azure Arc, there are some networking prerequisites that need to be met. The prerequisites are documented here in detail Prerequisites – SQL Server enabled by Azure Arc | Microsoft Learn
Some common errors when the prerequisites are not met are:
SSL Errors:
System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.
—> System.IO.IOException: Unable to read data from the transport connection:
A connection attempt failed because the connected party did not properly respond after a period of time, or established connection
failed because connected host has failed to respond..