Nothing to do with bridging settings, I'm afraid!
The auto-generation of supports is dependant on the combination of the bottom-facing area and width of the part and the settings used. Needless to say that in this case, the algoryth is not finding sufficient downward facing area per unit bed size to positively determine ithst support is needed.
Without any further information, I'm unable to help further......
Please supply a Factory file for this part.....and I'll be able to explain exactly why supports are not being auto-generated.