You have a setting in one of your programs set to 'Disconnect from the internet when (Download -Scan - Action) has completed.
You need to check frequently used programs (or possibly dial up settings) for a check box which indicates this behaviour.
Dell XPS 13 9370 (2018) review
No need to scan sketches into your computer with Moleskine's new smart pen
WWDC history: Apple's product launches since 2005
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