If you don't see recent messages in MightyText OR there appears to be a time gap in your message history on MightyText where no incoming or outgoing messages appear to have synced:

MightyText will pause syncing messages from your phone if you haven't used the product in the past 7 days. (either used the tablet app, web app, or Chrome Extension).

Messages will start syncing again once you start using MightyText (either the tablet app or web app)