Try the neutral basics:
"How are you?"
"How was your weekend?"
"Any plans for the holidays?"
See how they respond, with a bit of luck some of them will show traces of wit or humour, and you can go from there.
If they don't you can try showing some traces of humour or wit and see if anyone responds positively. Try not to whine, complain or depress people at the start even if you don't feel to cheerful.
Try and show genuine interest in their answers, actually, try and develop genuine interest if you really want it to work.
It make take a few days (weeks, months, years) before it feels natural.