Hi Ugo,
I had the same issue and I just managed to solve it by updating the software version of my UR16e robot.
Generally, this error happens when there is a mistake in the setup for Profinet on the TIA portal. GSD file, and the network setup on the robot. First of all, make sure the GSD file that you are using matches the version of the robot software.
The IP, and Profinet device name assigned to the robot can also be the problem. Please make sure the IP you assigned to the robot is unique in your network.
The following are several links to discussions about this issue. They might be helpful.