Can my newer version of the Seagull License Server work with my older version of BarTender?
BarTender 2019 and later
Yes and no.
A license server hosting a BarTender 2019 (or later) license will not be compatible with BarTender 2016 (or earlier) due to a protocol change
In BarTender 2019 and later, the license server is both forward and backward compatible. A BarTender 2019 client can connect to a BarTender 2021 server and vice versa.