Hello!
These can be caused by multiple problem. I will try to brake it down.
All APs seem to have lost contact with the VC and also show as down in Central. They are still broadcasting the SSID I created, however I can’t connect to them using either the web interface or CLI as the standard admin username and password are not accepted First of all, don't think of central as a mobility controller, but rather like Airwave. So its a management interface, which pushes configs to IAPs and switches and etc. So if your IAPs are offline in central, they can still be operational. It just means it lost contact. Second of all, if the IAPs contact central, and they are put into a group, they download that group config. If you want to access the vc or any other iap through console, you have to use the password that is configured for the IAP group under Wireless management->System->administrator.
Do the APs look for the VC by IP address? Have you configured a virtual IP for the VC? Have you statically set a Master? If not, then they will form the cluster and elect a master on their own.
All of the APs have been rebooted since losing the VC, but it seems they have not elected a new VC, which was my understanding of what should happen. If the IAPs are online, then you could go to monitoring->Online APs, and the IAP name that is in BOLD is the VC.
Also a few of the APs never came online in Central. They have been subscribed and are powered on (PoE) and connected to the LAN, showing two green LEDs. The two green leds indicate, that the AP is operational, and is broadcasting an SSID. It dosen't nescessarily mean the right SSID (SetMeUp perhaps?) In my experience, it is best to also register for an activate account, and sync that with aruba central. Its good for troubleshooting, since you can see if the device checks in to activate, and weather it gets the right provisioning rule. If the device dosen't even check into Activate, then there is a network or dhcp or dns problem. You could try console to IAP and the following:
34:fc:b9:cb:89:0e# show activate status
IAP MAC Address :XX:XX:XX:XX:XX
IAP Serial Number :CNCWJXXXXX
Cloud Activation Key :EQWEXXX
Activate Server :device.arubanetworks.com
Activate Status :success
Aruba Central Server :app1.central.arubanetworks.com
Last provision time :2018-09-17 11:41:33
Provision interval :10080 minutes
If activate provision dosen't succeed then its a network problem, or you haven't subscrived the equipment in central subscription assignment.
Speaking of dns, if you provision your IAPs with dhcp, and then give them a static IP, then don't forget to go to wireless management->system->general and set the dns. Because otherwise in case of a power outage, the IAPs try to reconnect to central using the Activate provisioniing rule, and they will try to resolve the fqdn of the activate server, but since the dns is not set for them, they will fail to reconnect.
In the Device Inventory screen in Central they have a grey dot rather than a green one. What does that indicate? Two of the three switches I added also have the grey dot. They are not online. If the name and IP is also not populated then they have never contacted Central. Otherwise it would be populated with the last accessed value.
Not sure I trust the web interface of Central. What's your experience been like? Don't trust the web interface :D It works with a pretty huge delay (5-10 minutes if its really bad). You can check if the device is online if you go to monitoring, click on the device name, then go to actions->console and if you can access your device, then its online. I experienced that the monitoring sometimes says that its offline, but I can console to it :) Also I experienced, that sometimes my equipment just goes offline all at onece, sometimes just segmets/clusters (had alerts configured) but they come back after 10 minutes. I check the monitoring->data usage, and if the data drops to 0 for some time, then you had service outage. If it is stable, then only the equipments had problem contacting central, but were functioning.
Daniel