Not really enough information to be sure, but usually a blue LED ( from the LED states FAQ) means a connection to your Era 100 came in via Bluetooth (including a new Bluetooth connection). This ‘new’ connection would normally interrupt either a WiFi or AirPlay 2 connection, since it is ‘new’ and presumed to be from a source the owner initiated.
How were you playing from your iPad before? Did you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it? They would likely to be able to give you specifics about what signals were received, as long as it was within the length of the storage for the diagnostic.