Hi,
No, you’re not the only one… there was a similar post 2 days ago here: Can not login to Battle net app
This forum is to provide feedback on the Battle.Net Desktop App – Blizzard rarely replies here so this isn’t a good place to ask for help.
A better place would be the Desktop App Tech Support forum:
Before posting there, however, you might want to check whether the troubleshooting suggested in the following Support article solves the issue for you:
Cheers !