So, I have the portal key to a level 1 portal that I "own". I went about 10KM to a level 4 to link to it. When I go to create the link, I select the key and click create. It SAID link successful, but when I look at the map it doesn't show up. I tried this at another nearby portal and the same thing happens. The portal key isn't in my inventory anymore, but if I force close the game and relaunch it shows up again.
To clarify: I only have the portal key to the destination portal. The origin portal is level 4, the dest portal level 1. The resonators on both portals are at anywhere from 40% to 80%
Best Answer
It happens if you've moved too fast between two portals according to Niantic policy :s.
It is a GPS cheater protection, BUT you don't have to cheat to activate this protection, a simple travel in a car can be too fast for Niantic.
It looks like Niantic servers compute an average speed between your last action on a portal and your current position, if this average speed is too high (and a few kilometers in car is enough to be too fast), you won't be able to do anything until the average is valid.
In the same time, you can't recharge resonators and hacking the portal will answer you "Hack acquired no items" and the burnout countdown will not start (you will be able to successively hack many times without getting anything else this message).
To correct this, I just wait a few more seconds (or minutes) until my hack will start the cooldown. Then, I can link, hack, recharge correctly.