We have released a potential temp fix for players being locked out - this is in the process of being pushed out.
One of the issues was caused by players having Season battles marked as their favourite (an odd one to cause problems) so we have pushed some data to change this in players accounts from Season battles as favourites to the Story battles.
If you notice this change, for now, we advise to not reselect Season battles as a favourite… it is also already displayed on the main screen 
This is an initial fix for one part of a number of issues at the moment, so if you still find you are locked out loading PQ3 due to black screen or generally cannot even launch - then unfortunately this was not the fix for your issue and the team is working to resolve these critical issues.