If your issue still isnt resolved then i apologise. After watching your video i have redone the blueprint nodes and functions to be exactly the same as yours and it works perfectly. I think its worth noting that i am using the First Person Shooter BP Template. That way i don’t have to touch the Pawn collision shapes and controls. I think if Glotty cant help you either, you should create a new test project using the First Person Shooter BP Template and try in there. If it works then post back here as that will eliminate a lot of things as the possible cause. Best of luck Ben.
Ok, now i understand whats happening. You are correct in that you did the item naming different, i didn’t set a default value i literally just typed it in the node, you dont have to keep it that way, you could setup a variable on your lightvial called “name” or something similar and expose it to the editor so its easily modifiable in the properties tab and likewise for the light set a “key” or “trigger item” (name it as you see appropriate) and expose it and link it in the correct place in the blueprint. its up to you how you handle that side of it.
that said, none of that was the problem, the issue is that the collision event is not triggering, which is strange as the vial gets destroyed even though the node is never triggered (unless there’s some crazy physics going on and it just launches through the floor on touch). The easy way to fix it would be to just use a trigger box instead of a collision capsule (mainly because i’ve not looked into collision detection enough to help you solve that issue) but zakman has covered the points i would have mentioned which may solve your issue in both cases.
Also congrats on pronouncing the nick correctly 
Dudes, it’s done! Y’hear me?! I’z DUNN! Computer says YES!
What joy is this? 
Okay, so seriously, first thing I did was delete everything. Then upgraded to 4.6 - now I don’t think it’s necessary, but good to have done anyway. I then simply opened a FPS BP Template to make sure the PlayerCharacter was correct set up, and first went through zakman186’s version. Zakman: since you put up those collision screenshots, they made all the difference.
When I knew zakman’s procedure worked, I deleted everything once again, and tried the same with Glotty’s version - and removing the triggerbox from the pickup and fixing the collision stuff - it too worked!
Now, I appreciate the templates, but if I can’t create my own stuff from ground-up, then I’m a lousy game designer in my own eyes. Thus, I started a clean project, created a player character from scratch and set everything up once again. After getting the different collisions wrong a few times and almost giving up, it finally worked. Perfection, it is.
As a great thanks to you and the community, I’ll create a video tutorial going through ALL the minute details in setting this up, making sure everything that can be misunderstood is addressed - even your grandma should be able to follow it, and come back to this thread and put it up. This way, anyone needing to know how to do this will have the entire solution easily accessible.
Again, thank you!
Good to hear, I’ll update the answer with the video when you post it.
Here’s the finished video tutorial: UE4 Tutorial | Use Keycard to Unlock Door - YouTube
Have a great day!
Added video to answer, you’ll have to set it as the correct answer again
oddly your question shows in the email i received but not here. You do not need additional interface blueprints, you just need to change the item’s name, so in my example for the keycard i use an overlap that calls add inventory and adds an item “keycard” class this as a unique identifier for that keycard, so another keycard could be “keycard2” etc. then in the door an overlap calls check inventory, in my example it checks for “keycard” which was the identifier i gave to the original keycard, so if there was another door for the second keycard (keycard2) then it would check for “keycard2” instead of “keycard”.
I thought I had deleted my questions after having re-read the topic and found the solution.
Thank you again for your help and your Reactivity