this problem is really confusing,
anyone can help?
There is a dependency on libsodium18. The dependency should have been installed, but was not and Sovrin is looking into what happen to that link in the last stable release. For now if you do an apt install libsodium18 you should be able to complete the installation.
Add libsodium18 to you package installs in both the agent.sh and validator.sh vagrant files before running vagrant up.
This walkthrough is still not completely bug-free though. For now, I would recommend using the docker option to get a test network up and running. you can use this process here: Make a test network with docker
I don’t know if this was resolved for you. On the master branch where the vagrant scripts are located there was a change to add in the libsodium18 install. It should be pushed to stable soon, but you can pull down the vagrant scripts from master and it should work.
The scripts are located here