The following dialog pops up and displays:
            The sever failed the authenticity check (file.vidcdn.pro)
Selecting either details-continue-cancel buttons all result in the same dialog appearing again
Any clues...?

EDIT
Couldn't find any filenames related to "vidcdn"
Was okay with simply doing a fresh install...
and--for now--that message has not appeared

Well that didn't last long...
Except this time it was another dialog albeit with the same title, i.e. Server Authentication - Plasma but for a different file
This time it's for the system tray weather widget, that gets the same fail message and also provides this additional info:



A rhetorical q: so why should the plasma server be failing on 5.13.1?
I never had this on 5.12...