Deleted server from Sophos Central, how do I put it back on the list?

HI Ingo , 

You cannot add the server with the installed Sophos AV, you would need to remove the AV from the system manually and then download an installer and proceed with installation . 

You could refer the KB article https://sophos.com/kb/124377  for removal steps . 

Thank you Aditya.  The section covering a Sophos Central Managed client solved the issue.  I had not found KB 124377 in my previous searches. 

As a side note, the temper protection module had been removed via Programs and Features so the two tamper protection registry entries (steps 5 and 6) did not exist.   However it was the disabling of Sophos AV service (along with the MCS agent registry entry)  that finally allowed me to successfully remove the product.

Thanks again.

HI Ingo , 

Thank you for an update , glad you are able to remove Sophos Endpoint from your system .