*In short: Call offline users on Skype to see if they’re actually online. They could appear offline because they’re invisible or due to glitches. *
I often plan to Skype with someone at a certain time, but they are not online at that time. I text them and ask them to get online, to which they reply that they already are.
This is because Skype has not tried to connect to them, it seems. To remedy this problem, give them a Skype call. If it goes through, they’re online. If it doesn’t, they’re offline.
This has the awkward disadvantage that, if they are online, it may seem that you’ve initiated a call for no reason. But this is a way to check if they’re online.
This also allows you to see if someone is invisible or actually offline.