WD 15, what to do if 2nd monitor not working

Just in case anybody else has this problem:
my second monitor, attached to a WD 15 docking station (and a Dell Precision 5550 laptop with windows 11) was suddenly not working. Win 11 did not recognize it anymore ("no additional display attached").

After trying different solutions, this one worked immediately:

* take the WD-15 off the wall plug
* wait for about 30 sec
* re-plug it into the wall socket
* (if necessary, also restart your laptop)