How can I get rid of the "MathWorks Software Deactivation Required" error?

I am using an academic license from my university, but today I found a message telling me that the license deactivation was necessary on my computer. I deactivated it producing the file I attached to this post, but did not copy and paste the string in the MATLAB network to deactivate the computer in the system, because then I saw that this warning could be a MATLAB bug and I am sure the academic license is still valid. I uninstalled my old version of MATLAB (r2019a) and installed another release (r2019b), and I found the same message after activating MATLAB.

I then tried to follow these steps:

https://www.mathworks.com/matlabcentral/answers/91951-why-do-i-get-a-deactivation-required-message-when-i-start-matlab

to deactivate and reactivate MATLAB, but after deactivating it, the license has a .deact extension and I cannot reactivate the product again, telling me that the license is invalid. I then tried to uninstall r2019b and install the latest release, r2020a, but I am back to square one again, with the same warning. This is strange because the activation after the installation works, the warning pops up after starting MATLAB. This time i closed the prompt and did nothing, and I can work normally. What am I supposed to do if I see the warning again?

Thanks in advance.