Opening version 3
Perhaps this should and one day will be How to... but for now this is a place we can link to help people having difficulties opening version 3. If you upgrade to version 3 and cannot open MuseScore try the following:
Double click a score to open MuseScore. If this works, open Edit->Peferences and remove the check from "Show start center". This should enable you to open MuseScore using the shortcut in the future.
Try running MuseScore from the command line using -w or -s on the command line. -w disables web view and -s disable the sound. See https://musescore.org/en/handbook/3/command-line-options for information on using command line options. Note that these need to be small letters, capital letters do other things. If 1 did not work and you are trying this option, I suggest that you start a new thread in the Bug and support forum so programmers can help you open MuseScore in the future and understand what the problem is.
Finally, try running MuseScore with the -R or -F command line option. Note that these are capital letters. You will get a warning that you are resetting MuseScore to factory settings with either of these options. This has been known to allow people to open MuseScore when otherwise it fails.
If someone has another method to open MuseScore, please add it to this thread. Other discussions should be started in new threads.