If it's not abundantly clear, Linkedin is not in love with tools like Super Send. They do not make it easy on us to provide a lovely experience. Occasionally getting disconnected comes with the territory.
Here are all the possible reasons why your Linkedin account might be getting disconnected frequently from Super Send:
Logging in / out from desktop or mobile
Logging in / out from a new location
Logging in / out of a new profile (perhaps a customer of yours)
Logging in from a new computer
Logging in on the mobile app
Not opening the chrome extension for > 2 weeks
Sending too many messages in a short period of time
Not visiting Linkedin for too long from the chrome profile where the super send extension is loaded
In short, there are 101 ways a Linkedin disconnection can happen.
Best practices:
Log in to Linkedin on the web with just one Linkedin profile in google chrome and then open the super send extension
Don't log out of Linkedin
Visit Linkedin once a week or at least once every two weeks.
Open the super send chrome extension once a week or once every two weeks.