make sure that you are connected to the internet and try again - pop up message

Looks to me an app is running in background. Have you checked your user to see if there are any auto start apps?

System Preferences > Users & Groups > [your user] > Login Items.

It might also be a remnant of an app that's been uninstalled. If you start in Safe Mode, you may be able to narrow down which it might be. Safe Mode doesn't load anything but the bare essentials to run the OS.

Start up your Mac in safe mode - Apple Support

Not familiar with the specific icon presented and since the user says basically nothing New has been installed on this machine ( have one myself - niece machine ) trying to identify the specific Application involved is akin to looking for a needle in a haystack.

The cut down on the search and to get a good look as to what is installed

Understand, we are all working Remotely from all around the world. 

Therefore, we do not have the On-Hands experience the User ( you ) have with this computer.

The next best thing for us to having a semi - actual On-Hand experience  with this computer is to follow the steps below

Download the Application Etrecheck directly from the Developer. 

The application is free or paid from added features. 

It will take a Snap Shot -  both the hardware and software.

 The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - using the Additional Text Icon ( 3rd Icon to last )

We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.