Norton Internet Security for 3 PC's

Yesterday the installation of NIS ended as described here:

https://community.norton.com/en/forums/norton-internet-sercurity-3-pcs

The error message appeared after it was as if someone took a screenshot from my desktop: the screen became black after which the browser (firefox) was reduced.

Today everything seems normal, although some functions are not active.  Please let me know if I have to ask for a solution.  Thanks.