I see that a link has appeared on the Indexing.FamilySearch.org News tab:
“If you receive an error while opening the application, click here and go through the steps provided. For questions or further assistance, please contact FamilySearch at 1-866-406-1830 in the U.S. and Canada (for international calls, click here), or by e-mail at firstname.lastname@example.org.”
I didn’t see this until after I called a Support missionary – but the helps in this link worked for me!
The link is to a knowledge document 103791 – with an attached tool to remove partially installed versions of the new application
Please reach out and help all the people you know who do Indexing – check to see they are OK