Tips drop in a ten level range; 10-19, 20-29, etc. When you outlevel a range, all the tips you had before are deleted, and you need to collect new ones. Since you are level 40, you might not have had any drop since they were last deleted.
When you get a tip, you will see a yellow pop-up, like the ones for recipes, salvage,etc. Watch for that, and then check your tip window.
Not having Tipped Off implies that you've never had one drop at all though. I can only think of two reasons for that:
-You're a Praetorian and stayed in Praetoria doing Night Ward and First Ward rather than taking the mission to go to Primal Earth and become a Hero or Villain. Praetorians can't get tips until they leave Praetoria and puck a side.
-You've leveled solely in AE with AE rewards (tickets) rather than standard rewards. AE rewards will not grant tickets. Even if you have standard rewards selected, I'm not sure if AE will drop tips.
If neither of those are the case, I have no idea gow you got to 40 without any tips dropping.