You try to connect to an agent and fail with the following error:
"Could not connect to...The connection attempt lasted for a time span...target machine actively refused it"
The Console is trying to connect to an agent, but the agent's service is down.
In addition, the "Deploy agents automatically" (in agent's settings) is disabled, so when you click connect, the Console will try just to connect, and if the agent's service is down, it will fail.
In order to fix this issue, the Console will need to start the agent's service while trying to connect.
You can manually "Upgrade Remote Agent", from Agent Control, or use the "Deploy agents automatically" option, to automatically try to restart the agent's service when you connect.
If the the "Deploy agents automatically" is checked\enabled, the monitor might have high resources consumption.
There are situations where there are many computers that the monitor cannot connect to (network issue, server is down etc).
In these situations, the monitor will try upgrading them again and again, an action which might take high CPU\Memory.