Usually, it happens even you are offline, Viber says you are online. It may be because of device error or the problem in the version. If you have an old version, it may show incompatibility and when you are offline it shows you online.
In that situation upgrade your phone or uninstall the Viber app and reinstall it. If any bugs present or the portion of the app is corrupted it will be resolved and you will not find such error again. Try this method now and you will not get such an issue.
