I am currently mentoring/supervising a person within an academia-related field. This is not my first time in this role. I am easygoing, dislike unnecessary conflicts, and I like people to feel good and have nice teamwork. I highly value communication so I am open (and encourage others) to report so I can better help/work with them. I'd say I'm rather 'normal' in this sense (no micromanaging, no strict rules, adaptable to different styles).
So, there is this person currently under my guidance. I don't directly pay his salary (I pay all the other costs), but his project was approved because I was recommended to be the supervisor. It started very well and we both agreed communication should exist at all times (I consider this obvious but just in case I make it clear before choosing a candidate).
However, for unknown reasons, everything changed when the real work started. He seems constantly in a defensive position and I hardly have any news from him. I tried to consider different scenarios: Maybe I am doing something wrong? Maybe he doesn't want to bother the mentor? Etc. He seems to purposely limit the information to me. Unfortunately, the opportunities (of synergy and creative spin-offs) that are lost due to this lack of interaction will result in a loss for the project and for his career.
I constantly try to reach him with very limited success.
He's not lazy, or incompetent, nor doesn't want the project to advance. But, without explicit reasons, he doesn't follow my advice or communications. I am open to the possibility that my advice might not be appropriate for any reason, and to discuss it. Basically, he puts very little (if any) effort into keeping the communication alive and I am concerned about how healthy it is to work like this.
Recently, I had to travel for a few weeks to work in another city. He wanted to do some activities while I was absent and I suggested he wait until I arrive so I can participate and help him better. He decided to go on anyway, and I was fine with that. Five weeks later (with no news, as usual) I started getting (unsolicited) updates about him from other colleagues: while I was away he was spreading the 'image' (I can't be sure what words he used) that I left him alone, abandoned with his activities. He even said that if I don't help him soon, he will make sure that I don't get any credit for any advancement in the project. Similarly, he was engaging in trying to set up formal agreements with another company, without me (ie his formal supervisor) knowing anything about it.
This is something that builds up a barrier between us and for some reason, I feel something like discomfort from his side (which I have asked about and again, never got a real answer).
This is the first time I have had to deal with this stuff. I feel like I don't have the tools to handle him or the situation. In one of my intents to know what was happening, I asked him if there was anything from my side that he felt was blocking or preventing the communication (no answer to that) and that I was willing to change things if needed.
So, as you see, the title of this question is about communication, but can it be something else? What would you do in my place? How to solve this professionally without blocking his career but at the same time keeping my authority? I fear that if I don't do anything and let him spread bad words about me I will pay an undeserved cost: it will hurt my reputation because it would look like a double standard from my side (ie always preaching about communication and team work but on the other hand I 'abandon' my employee instead).
Edit 0: reduced the length of the text, as suggested by some commenters.