Wanyama, who is rated in the £12m bracket, was close to a move to St Mary's earlier this month after a transfer fee was agreed but the deal reportedly broke down due to a failure to settle personal terms.
Southampton, though, have not given up their pursuit of the Kenyan star and, after Saturday's 2-1 friendly defeat by Cluj, Lennon has confirmed an offer to Celtic still exists.
"I had a chat with Victor and he's a wee bit confused but what we gather is that Southampton have re-ignited their interest," said Lennon in the Sunday Mail.
"They've shown an interest again and the bid is there. It's all about the negotiations between Saints and the agent now. I'd imagine that might get the ball rolling again.
"I've only seen Victor for a couple of days but he trained with the rest of the squad who didn't play against Cluj.
"If nothing materialises, he'll play some of the friendly game on Tuesday against Greuther Furth."