Yes it's the headphone jack (many Fender amps with the 1/8 jack have this problem). Just try to plug and unplug the headphones many times and if the amp works without headphones don't use headphones anymore ...
Thanks for this great software, is there a way to convert the B3 files to use with a B1on ? I think the B3 files are xml but I have no idea for the B1on files.