Signal users are experiencing issues around the world, with users unable to send and receive messages. Signal has acknowledged the reports and they’re trying to restore service as quickly as possible. It is not known if this is planned maintenance activity, a problem with their servers, or if the networks are under heavy load as more users are migrating from WhatsApp. The problem was first reported at 10:09 AM EST. Signal is now back online and users will have to wait until the company has resolved the issue.
Source: https://www.bleepingcomputer.com/news/software/signal-down-after-getting-flooded-with-new-users/