If you have problems signing in to Destiny then it’s a common problem because many people are reporting that they get “Destiny servers not available” message.
Bungie is also looking into this issue and have put up a disclaimer on their website.
This should be a temporary problem since PSN went down and came back up and that could have caused some issues.
If you still cannot log into Destiny but see your friends are logged in, you can try mashing the x button on the DualShock 4 when you try to login, and if you still can’t then wait for Bungie to fix it.
We will keep you updated once we hear more on this. Stay tuned to GC.