Identify which connected product you have
A standalone smart hub and an opener with built-in Wi-Fi do not necessarily follow the same troubleshooting sequence. Record the model and the exact app message, with any private account information removed from screenshots. Tell the service contact whether the wall station and handheld remote still work normally and whether the displayed door position appears current.
Start with the recent change
A new router, changed Wi-Fi name or password, or interrupted internet service can explain a loss of connection. Chamberlain Group gives separate guidance for hubs and built-in Wi-Fi openers. Use the instructions for the actual product; a general factory reset can remove useful setup and should not be the first response to every offline message.
Keep the physical door in view
An old app status should not be treated as confirmation that the garage is secure. Verify the physical position safely when possible, and make separate access arrangements if the app is your usual control. If the door binds, reverses abnormally or has visible damage, treat that as a door-service concern even if the network also needs attention.
Your questions
Can I use a local control while the app is offline?
If the door is mechanically sound and the installed system supports normal local operation, follow its instructions using a working control with the opening in view. An offline app alone does not establish a mechanical failure; do not operate a damaged or unstable door.
Can an app outage mean all remotes are erased?
Not necessarily. Local radio access and connected accounts use different functions; report which controls still operate rather than assuming a total reset is required.