Agree silverraven0 -- "being from the 1300s" isn't a character trait so much as an indicator of background knowledge, values, and culture -- which is also going to be dependent on where exactly they're from and what beliefs they hold.
So like, Amberday brought up the witch-hunt thing -- from what I can tell, there certainly were people getting accused of witchcraft at that point in time, BUT, also in the early 1300s the official stance of the church was that witches aren't real so you shouldn't prosecute people for that. You could have two people from the same time period and have one of them believe that witches are the source of all of life's unexplained woes, and the other believe that "witches" are superstitious nonsense that no God-fearing person would believe in.
So there's a couple of questions in here -- one is "how will this character react to the unexpected and unexplainable?" which is almost entirely dependent on that character's personality and values. You could ask the same question of a character from any time period!
The other question is "what's going to be unexpected and unexplainable for this character, based on their background?" and that's honestly gonna require looking specific stuff up. If you want to know what they think of cell phones, you're gonna have to look up how communications were sent in the 1300s and determine what level of literacy you feel like was normal for the specific lifestyle of your character in that time period and figure out, from the base they're working from, what's going to be understandable and what's going to seem mystical? And then you look back at their personality again to determine how much they're willing to accept a miraculous device that's beyond their understanding as a human innovation.
I don't think there would be an across-the-board reaction to all Technology -- it's probably going to depend on which things are similar to something they know, and which things are completely alien!