Please be aware that, at this time, stack member devices can only be registered into Active Advisor by either using the web or desktop scanner using traditional access methods (HTTPS/SSH/TELNET/HTTP), or by manually uploading the devices into Active Advisor via spreadsheet or via "show" commands (see the Tools section of Active Advisor). Master devices scanned via SNMP will only register the master device, as stack member details are not discovered by the scanner via SNMP protocol.
The chosen Active Advisor scanner will attempt to log into your devices and retrieve the output of several privileged commands, such as 'show running-config', from which the device's enabled features, and host name are learned.
The scanner will presently only wait a few dozen seconds for a command to start issuing output before it gives up and moves on to the next command in a list of commands to be tried. Some device configurations (and stacks of devices) can take several seconds, to several minutes, in order to produce the output for 'show running-config'.
As these commands are consider low-priority by IOS, high CPU load (show proc cpu hist) can also affect the time it takes to generate the running-configuration.
It's worth noting that although such commands as 'show running-config' may cause the CPU load to climb or reach 100% on a device, the CPU time given to these low-priority processes are preempted by other higher-priority processes, as to not impact packet processing.
If you experience an extremely long delay when running "show running" commands on your stack, there may be a workaround available to you depending on the IOS or IOS-XE version your devices are running. Please see the documents below about enabling 'parser config cache interface' in your running-config, which can dramatically speed up low-priority NVGEN-type commands such as 'show running-config':
Please note that after enabling the command, you should perform a 'show running-config' once in order to establish the cache. Subsequent executions (including by an Active Advisor scanner) are then able to speed up significantly (and automatically) by the presence of the cache.