SA-0005 when trying to add a W2019 server to SupportAssist Enterprise

I have 7 physical servers, and all of them are now at Windows 2019 Standard. I installed Server Assist Enterprise on a Dell R720xd server. I then attempted to add the other 6 servers. 5 added just fine. The sixth one is giving a SA-0005 error:

SupportAssist Enterprise is unable to add the device 192.168.1.122 because an attempt to connect to the device is unsuccessful.

Make sure that both the system running SupportAssist Enterprise and the device you are trying to add are connected to the same network, and then retry adding the device.

Error code:SA-0005

These systems are on the same domain, in the same rack, and have access to each others drives. They are definitely on the same network. Adding the device again produces the same error.